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1

Statistical initial orbit determination

For the ballistic missile initial orbit determination problem in particular, the concept of 'launch folders' is extended. This allows to decouple the observational data from the initial orbit determination problem per se. The observational data is only used to select among the possible orbital element sets in the group of folders. Monte Carlo simulations using up to 7200 orbital element

L. G. Taff; B. Belkin; G. A. Schweiter; K. Sommar

1992-01-01

2

Statistical initial orbit determination

The computation of a meaningful initial orbital element set based on angles- only data is abandoned as a futile endeavor. Rather, for the ballistic missile initial orbit determination problem in particular, the concept of 'launch folders' is extended. This allows one to decouple the observational data from the initial orbit determination problem per se. The observational data is only used

Laurence G. Taff; Barry Belkin; G. A. Schweiter; K. Sommar

1991-01-01

3

A new method of initial orbit determination

NASA Astrophysics Data System (ADS)

A new method of initial orbit determination for angles-only data is presented. The technique is applicable with only three data sets but the formalism can incorporate arbitrarily large amounts of data. The algorithm rests on the fact that the orbital plane is usually very well determined, as a consequence of the central nature of the gravitational force, and a theorem of Hamilton's from 1846. His result states that the velocity vector describes a circle in the orbital plane in a particular manner. Tests on a variety of deep-space artificial satellites show that the method has promise. Unfortunately it does not work very well on the stressing cases of current practical application - high eccentricity orbits.

Morton, B. G.; Taff, L. G.

1986-06-01

4

A method of initial orbit determination for long arc data

NASA Astrophysics Data System (ADS)

According to the principles of the unit vector method (UVM), a method of initial orbit determination for long arcs is presented. This method is applicable not only to long arc data but also to short arc data and is suitable for earth satellites with arbitrary orbital eccentricity and inclination. This method has a good accuracy of initial orbit determination and good convergence. It offers a basis for extending the application of the UVM method from initial orbit determination to orbit improvement.

Lu, Ben-kui; Ma, Jing-yuan; Xia, Yi; Zhang, Yang

5

A method of initial orbit determination for long arc

NASA Astrophysics Data System (ADS)

According to the principle of the unit vector method, (UVM), a method of initial orbit determination for long arc is presented. This method is applicable to not only long arc but also short arc. It suits for different kinds of observational data and the artificial earth satellites with any orbital eccentricity and inclination. In addition, this method is beneficial to the accuracy of initial orbit determination and the convergence of algorithm. Especially, it offers a basis to extend the application of the UVM method from the initial orbit determination to the orbit improvement.

Lu, B. K.; Ma, J. Y.; Xia, Y.; Zhang, Y.

2003-11-01

6

Resurrection of Laplace's Method of Initial Orbit Determination.

National Technical Information Service (NTIS)

This report deals with a number of interrelated topics. The common thread is Laplace's method of initial orbit determination based on passively acquired optical data. We discuss this method's principal competitor (that of Gauss), the difficulties of Gauss...

L. G. Taff

1983-01-01

7

The use of angles and angular rates. II - Multiple observation initial orbit determination

Earlier work on the angles and angular rate initial orbit determination problem has been extended to allow the incorporation of arbitrary amounts and mixtures of angles and angular rate data. The statistical estimation technique used is that of Maximum Likelihood. Numerical test on six widely different satellite orbits indicate that the orbital elements can generally be computed to 1% from

L. G. Taff; D. L. Hall

1980-01-01

8

On the optimal accuracy and double solutions of initial orbit determination

The optimal accuracy and quasi-optimal algorithm of determining the initial orbit solely with the short-arc measuring angle is investigated on the basis of the theory of optimal statistics. There exists the Cramer-Rao lower bound for the theoretical accuracy of general parameters' estimation. For initial orbit the Cramer-Rao lower bound has its optimal accuracy. For the case of small eccentricities, the

Peizhang Jia; Lianda Wu

1998-01-01

9

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

10

Statistical methods for determining satellite trajectories after being put into orbit, after changes in the trajectory and at regular intervals during orbital lifetime are outlined. The least squares method, a differential Gauss-Newton correction algorithm, and interpretation of the results are introduced.

P. Legendre

1984-01-01

11

ICESat Precision Orbit Determination

NASA Astrophysics Data System (ADS)

Following the successful launch of the Ice, Cloud and land Elevation Satellite (ICESat) on January 13, 2003, 00:45 UTC, the GPS receiver on ICESat was turned on successfully on Jan. 17, 2003. High quality GPS data were collected since then to support Precision Orbit Determination (POD) activities. ICESat carries Geoscience Laser Altimeter System (GLAS) to measure ice-sheet topography and associated temporal changes, as well as cloud and atmospheric properties. To accomplish the ICESat science objectives, the position of the GLAS instrument in space should be determined with an accuracy of 5 cm and 20 cm in radial and horizontal components, respectively. This knowledge is acquired by the POD activities using the data collected by the GPS receiver on ICESat and the ground-based satellite laser ranging (SLR) data. It has been shown from pre-launch POD studies that the gravity model error is the dominant source of ICESat orbit errors. The predicted radial orbit errors at the ICESat orbit (600 km altitude) based on pre-launch gravity models, such as TEG-4 and EGM-96, are 7-15 cm. Performance of these gravity models and the recent gravity models from GRACE on ICESat POD were evaluated. The radial orbit accuracy is approaching 1-2 cm level with the GRACE gravity model. This paper also summarizes POD activities at Center for Space Research (CSR), which is responsible to generate ICESat POD products.

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

2003-12-01

12

Initial Statistical Ranging of Orbits for Trans-Neptunian objects

We consider initial determination of orbits for Trans-Neptunian objects (TNOs), a topical theme because of the rapidly growing TNO population and the challenges in recovering lost TNOs. We apply the method of initial phase-space ranging of orbits to the poorly observed TNOs. The a posteriori probability density of the TNO orbital elements can be highly complicated, and the covariance matrix

K. Muinonen; J. Virtanen; E. Bowell

2000-01-01

13

Interplanetary orbit determination

NASA Technical Reports Server (NTRS)

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

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

1973-01-01

14

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

15

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

16

NASA Astrophysics Data System (ADS)

Precise orbit determination (POD) is a key factor to enable phase referencing observations with Astro-G. A POD accuracy of 30 cm is required for efficient X-band phase referencing observations, accuracy of 6 cm for K-band observations, and accuracy of 3 cm for Q-band observations. For the POD, Astro-G will be equipped with a GPS/Galileo receiver and a SLR (Satellite Laser Ranging) retroreflector array. Four POD antennas will be equipped on four sides of the satellite body, to cover all directions. The SLR will be used as a complement to the GPS at middle-to-high altitude. Because the refroreflector array should always face to the Earth direction, it will be set up on the Ka-link antenna gimbal. The most significant perturbing force for the Astro-G is solar radiation pressure (SRP). The reflectivity of each surface component should be preliminary measured in detail to model the SRP. The estimated achievable POD accuracy at apogee is 10 ˜ 30 cm in nominal case. Phase referencing observations in K- or Q-band can be performed if the enough amount of SLR tracking data can be obtained at high altitudes.

Takeuchi, H.; VSOP-2 Orbit Determination Sub-Working Group

2009-08-01

17

Spitzer Orbit Determination During In-orbit Checkout Phase

NASA Technical Reports Server (NTRS)

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

Menon, Premkumar R.

2004-01-01

18

Orbit determination: Statistical methods

The problem of finding a satellite trajectory from position and\\/or velocity measurements taken at a given instant in time is examined. A trajectory evolution model including a random vector which represents measurement error is presented. Assuming an iterative approach, the problem is linearized using a previous orbital position estimation. The least squares method is considered in terms of the linear

P. Legendre

1980-01-01

19

Geostationary orbit determination using SATRE

NASA Astrophysics Data System (ADS)

A new strategy of precise orbit determination (POD) for GEO (Geostationary Earth Orbit) satellite using SATRE (SAtellite Time and Ranging Equipment) is presented. Two observation modes are proposed and different channels of the same instruments are used to construct different observation modes, one mode receiving time signals from their own station and the other mode receiving time signals from each other for two stations called pairs of combined observations. Using data from such a tracking network in China, the results for both modes are compared. The precise orbit determination for the Sino-1 satellite using the data from 6 June 2005 to 13 June 2005 has been carried out in this work. The RMS (Root-Mean-Square) of observing residuals for 3-day solutions with the former mode is better than 9.1 cm. The RMS of observing residuals for 3-day solutions with the latter mode is better than 4.8 cm, much better than the former mode. Orbital overlapping (3-day orbit solution with 1-day orbit overlap) tests show that the RMS of the orbit difference for the former mode is 0.16 m in the radial direction, 0.53 m in the along-track direction, 0.97 m in the cross-track direction and 1.12 m in the 3-dimension position and the RMS of the orbit difference for the latter mode is 0.36 m in the radial direction, 0.89 m in the along-track direction, 1.18 m in the cross-track direction and 1.52 m in the 3-dimension position, almost the same as the former mode. All the experiments indicate that a meter-level accuracy of orbit determination for geostationary satellite is achievable.

Lei, Hui; Li, ZhiGang; Yang, XuHai; Wu, WenJun; Cheng, Xuan; Yang, Ying; Feng, ChuGang

2011-09-01

20

Choosing the Initial LISA Orbital Configuration

NASA Astrophysics Data System (ADS)

The Laser Interferometer Space Antenna (LISA) mission proposes to detect gravitational radiation by synthesizing one or more interferometric gravitational wave detectors from fringe velocity measurements generated by chances in the light travel time between three spacecraft in a special set of drag-free, circumsolar orbits. Once the spacecraft are set in their orbits the orientation of the LISA interferometers at any further time is fixed by the Kepler Laws and the initial orientation of the spacecraft constellation. The initial orientation does not affect those locations on the sky where LISA has greatest sensitivity to gravitational waves; however, it does affect those locations where nulls in the LISA response to gravitational waves fall. By artful choice of the LISA initial orientation we can thus choose to optimize LISA's sensitivity to sources or groups of sources whose location (eg., the galactic center or plane, nearby globular cluster, etc.) may be known in advance. )

Jani, Karan; Finn, Lee Samuel; Benacquista, Mathew

2010-02-01

21

A new method for orbit determination: Unit vector method

NASA Astrophysics Data System (ADS)

In this paper, a method of orbit determination is presented according to the principle of unit vector method (UVM). The model and arithmetic are improved and it not only suits initial orbit determination with short arc data, it also suits orbit improvement with data longer. It is also suitable for orbit of any eccentricity and any inclination. It omits most partial derivatives of all the elements which must be calculated in classical differential orbit improvement (DOI), so, it is more efficient than DOI, and the accuracy of orbit determination and convergence of algorithm are also improved appreciably.

Zhang, Jing; Lu, Benkui; Ma, Jingyuan; Xia, Yi; Zhang, Yang

2009-07-01

22

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

23

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

24

TDRS orbit determination by radio interferometry

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

Michael S. Pavloff

1994-01-01

25

Calibration effects on orbit determination

NASA Technical Reports Server (NTRS)

The effects of charged particle and tropospheric calibrations on the orbit determination (OD) process are analyzed. The calibration process consisted of correcting the Doppler observables for the media effects. Calibrated and uncalibrated Doppler data sets were used to obtain OD results for past missions as well as Mariner Mars 1971. Comparisons of these Doppler reductions show the significance of the calibrations. For the MM'71 mission, the media calibrations proved themselves effective in diminishing the overall B-plane error and reducing the Doppler residual signatures.

Madrid, G. A.; Winn, F. B.; Zielenbach, J. W.; Yip, K. B.

1974-01-01

26

GOSAT initial on-orbit results

NASA Astrophysics Data System (ADS)

The Greenhouse gases Observing SATellite (GOSAT) is a satellite to monitor the carbon dioxide (CO2) and the methane (CH4) globally from space. It is a joint project of Japan Aerospace Exploration Agency (JAXA), Ministry of the Environment (MOE) and National Institute for Environmental Studies (NIES). GOSAT will be placed in a 666 km sun-synchronous orbit of 13:00 local time, with an inclination angle of 98 deg. It will be launched on January 21, 2009. Two instruments are accommodated on GOSAT. Thermal And Near infrared Sensor for carbon Observation Fourier-Transform Spectrometer (TANSO-FTS) detects the Short wave infrared (SWIR) reflected on the earth's surface as well as the thermal infrared (TIR) radiated from the ground and the atmosphere. TANSO-FTS is capable of detecting wide spectral coverage; three narrow bands (0.76, 1.6, and 2 micron) and a wide band (5.5-14.3 micron) with 0.27 cm-1 spectral resolution. TANSO Cloud and Aerosol Imager (TANSO-CAI) is a radiometer of ultraviolet (UV), visible, and SWIR to correct cloud and aerosol interference. The presentation includes the instrument design, pre-launch test results and onboard calibration schemes; as well as, the initial on-orbit results.

Hamazaki, T.; Nakajima, N.; Kuze, A.; Suto, H.; Kawakami, S.; Shiomi, K.

2009-04-01

27

Champ precise orbit determination using GPS data

Precise CHAMP orbits have been computed in the framework of the IGS\\/LEO CHAMP Orbit Comparison Campaign for a period of 11 days in May 2001. A reduced-dynamic orbit determination strategy has been applied based on ionospheric-free triple-differenced GPS phase measurements along with precise GPS orbits computed by the International GPS Service (IGS). The resulting CHAMP orbit accuracy is assessed using

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

2003-01-01

28

Classical and modern orbit determination for asteroids

NASA Astrophysics Data System (ADS)

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

Gronchi, Giovanni F.

2005-04-01

29

TDAR (Telescopic Detection And Ranging): Preliminary Orbit Determination.

National Technical Information Service (NTIS)

The note analyzes the procedures for preliminary orbit determination based on sparse data from the TDAR system Error analyses of the initial orbit generation in the case of the single-telescope and parallax schemes are performed. A model for the angular e...

R. idharan

1973-01-01

30

Precision Orbit Determination for the Lunar Reconnaissance Orbiter

NASA Astrophysics Data System (ADS)

The Lunar Reconnaissance Orbiter (LRO) spacecraft was launched on June 18, 2009. In mid-September 2009, the spacecraft orbit was changed from its commissioning orbit (30 x 216 km polar) to a quasi-frozen polar orbit with an average altitude of 50km (+-15km). One of the goals of the LRO mission is to develop a new lunar reference frame to facilitate future exploration. Precision Orbit Determination is used to achieve the accuracy requirements, and to precisely geolocate the high-resolution datasets obtained by the LRO instruments. In addition to the tracking data most commonly used to determine spacecraft orbits in planetary missions (radiometric Range and Doppler), LRO benefits from two other types of orbital constraints, both enabled by the Lunar Orbiter Laser Altimeter (LOLA) instrument. The altimetric data collected as the instrument's primary purpose can be used to derive constraints on the orbit geometry at the times of laser groundtrack intersections (crossovers). The multi-beam configuration and high firing-rate of LOLA further improves the strength of these crossovers, compared to what was possible with the MOLA instrument onboard Mars Global Surveyor (MGS). Furthermore, one-way laser ranges (LR) between Earth International Laser Ranging Service (ILRS) stations and the spacecraft are made possible by the addition of a small telescope mounted on the spacecraft high-gain antenna. The photons received from Earth are transmitted to one LOLA detector by a fiber optics bundle. Thanks to the accuracy of the LOLA timing system, the precision of 5-s LR normal points is below 10cm. We present the first results of the Precision Orbit Determination (POD) of LRO through the commissioning and nominal phases of the mission. Orbit quality is discussed, and various gravity fields are evaluated with the new (independent) LRO radio tracking data. The altimetric crossovers are used as an independent data type to evaluate the quality of the orbits. The contribution of the LR data is assessed. Multi-arc solutions over entire months are presented, which allow to strengthen the LR data because fewer clock-related parameters need to be adjusted. Finally, a preliminary 1-month solution with altimetric crossover constraints is evaluated and discussed

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

2010-05-01

31

Precise Method of Orbit Height Determination

NASA Astrophysics Data System (ADS)

The problem of satellite orbit determination is a very important one, you can determine the orbit height of a low Earth orbiting (LEO) artificial satellite by using the satellite's apparent travel when the satellite appears to be near your local zenith, Or for most precise between two points of observation in earth. By using the determined orbit height, you can also determine the approximate orbit period of the satellite, this method takes advantage of the fact that the satellite's true velocity can be seen when it is nearly overhead. This paper illustrate how to obtain the height of the satellite using two observers method and by using MATLAB program then comparing this method with one observer method and illustrating how to increase the accuracy and take the measurement not limited to the local zenith only, but to any place of the orbit if you have an estimated period time for the satellite also these calculations depends on the data from NASA site.

Elbanna, Ahmed

32

Orbit determination by range-only data.

NASA Technical Reports Server (NTRS)

The determination of satellite orbits for use in geodesy using range-only data has been examined. A recently developed recursive algorithm for rectification of the nominal orbit after processing each observation has been tested. It is shown that when a synchronous satellite is tracked simultaneously with a subsynchronous geodetic target satellite, the orbits of each may be readily determined by processing the range information. Random data errors and satellite perturbations are included in the examples presented.

Duong, N.; Winn, C. B.

1973-01-01

33

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

34

Determination and prediction of Magellan's orbit

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

35

Precision Orbit Determination for the Lunar Reconnaissance Orbiter

NASA Astrophysics Data System (ADS)

The U.S. Lunar Reconnaissance Orbiter (LRO) mission will be launched in October 2008, and will carry out a detailed mapping of the Moon using a science payload of multiple instruments, including the Lunar Orbiter Laser Altimeter (LOLA), and the Lunar Reconnaissance Orbiter Camera (LROC) (Chin, 2007). One of the primary goals of the LRO mission is develop a geodetic grid for the planet. A subsidiary goal is the improvement of the lunar gravity field. The environment for POD on LRO is especially challenging. The spacecraft will orbit the Moon at a mean altitude of 50 km, and the expected error from the Lunar Prospector series of gravity models (to degree 100 or to degree 150) can be expected to be hundreds of meters. LRO will be tracked by S Band Doppler from White Sands, New Mexico, and Dongara, Australia, as well as by one-way laser ranging from Satellite Laser Ranging (SLR) tracking stations on the Earth. However, unlike the Japanese lunar mission SELENE (Kaguya), no direct tracking will be available while the spacecraft is over the lunar farside. We review the status of orbit modelling for LRO, for both the geopotential modelling and the nonconservative force models, as well as anticipated improvements. We discuss the modelling for the one-way laser ranging observable, and how the data from the one-way laser ranging (LR) system will be acquired from selected stations of the global stations of the SLR network. We discuss the orbit determination strategies which we expect to implement on this mission, including the use of altimeter crossovers from the LOLA instrument to supplement the Earth-based tracking and we review the projected orbit determination accuracies that will be attainable.

Lemoine, Frank; Rowlands, David; McGarry, Jan; Neumann, Gregory; Chinn, Douglas; Mazarico, Erwan; Torrence, Mark

36

Errors in orbit determination of artificial satellites

The influence of position measurement errors upon determination of satellite orbital parameters and the effect of errors in orbital parameters on the prediction of satellite positions are numerically evaluated. All calculations refer to a representative number of various trajectories. An expectation window is defined for an area in space in which an investigated satellite may be picked up again one

R. Deriz

1976-01-01

37

Spacecraft orbit determination using GPS navigation solutions

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

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

2000-01-01

38

TDRS orbit determination by radio interferometry

NASA Technical Reports Server (NTRS)

In support of a NASA study on the application of radio interferometry to satellite orbit determination, MITRE developed a simulation tool for assessing interferometry tracking accuracy. The Orbit Determination Accuracy Estimator (ODAE) models the general batch maximum likelihood orbit determination algorithms of the Goddard Trajectory Determination System (GTDS) with the group and phase delay measurements from radio interferometry. ODAE models the statistical properties of tracking error sources, including inherent observable imprecision, atmospheric delays, clock offsets, station location uncertainty, and measurement biases, and through Monte Carlo simulation, ODAE calculates the statistical properties of errors in the predicted satellites state vector. This paper presents results from ODAE application to orbit determination of the Tracking and Data Relay Satellite (TDRS) by radio interferometry. Conclusions about optimal ground station locations for interferometric tracking of TDRS are presented, along with a discussion of operational advantages of radio interferometry.

Pavloff, Michael S.

1994-01-01

39

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

40

Mars Exploration Rover cruise orbit determination

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

41

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

42

Champ orbit determination and gravity field recovery

NASA Astrophysics Data System (ADS)

Results are presented from precise orbit computations of CHAMP using a reduced dynamic procedure within the GIPSY/OASIS software. Details are given of the orbital strategy and tuning process for the kinematic stochastic accelerations. The accuracy of the orbits is quantified by overlap residuals, by comparison against independent orbits submitted to the IGS LEO Pilot Project and by use of SLR tracking. GPS derived Cartesian positioning is used as tracking to recover scaling factors and offsets for the accelerometer data, thruster mismatch and misalignment, and gravity field harmonics. A comparison is undertaken of surface forces inferred from the accelerometer data and from modelling. Selected sets of CHAMP positioning and accelerometer data are then used to derive an enhanced gravity field. Precise orbit determination of geodetic and altimetric satellites are compared against existing models and the new field, NCL_champ.2.

Moore, P.; Turner, J. F.; Qiang, Z.

2003-04-01

43

New determination of the orbit of Miranda

Determinations of the orbital elements of Miranda, the innermost satellite of Uranus, which were made subsequent to the determinations of Whitaker and Greenberg (1973) are reported. The present determination is based on observations made during the 1975 and 1977 oppositions with the 155-cm astrometric reflector at Flagstaff Observatory, and during the successive oppositions of 1977, 1978 and 1979 with the

C. Veillet

1981-01-01

44

Orbit determination methods in view of the PODET project

NASA Astrophysics Data System (ADS)

We present an orbit determination method based on genetic algorithms. Contrary to usual estimation methods mainly based on least-squares methods, these algorithms do not require any a priori knowledge of the initial state vector to be estimated. These algorithms can be applied when a new satellite is launched or for uncatalogued objects We show in this paper preliminary results obtained from an SLR satellite, for which tracking data acquired by the ILRS network enable to build accurate orbital arcs at a few centimeter level, which can be used as a reference orbit. The method is carried out in several steps: (i) an analytical propagation of the equations of motion, (ii) an estimation kernel based on genetic algorithms, which follows the usual steps of such approaches: initialization and evolution of a selected population, so as to determine the best parameters. Each parameter to be estimated, namely each initial keplerian element, has to be searched among an interval that is preliminary chosen.

Deleflie, F.; Coulot, D.; Decosta, R.; Richard, P.

2013-11-01

45

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

46

Seasat orbit determination from laser range observations

It is pointed out that the Seasat ocean monitoring satellite was the first American satellite designed specially for oceanographic observations. The satellite was launched on June 26, 1978, into a near-circular orbit at an altitude of about 790 km and with an inclination of 108 deg. The Altimeter\\/Precision Orbit Determination Experiment (ALT\\/POD) was one of the main experiments performed with

K. F. Wakker; B. A. C. Ambrosius; T. van der Ploeg

1983-01-01

47

Method of orbit determination for short Arc of lunar probe transfer orbit

The orbit determination without initial information and mono-parameter iteration is discussed. An approximate analytical solution which shows accurate status is required for the dynamic model utilized in this method. The motion of the Lunar probe into the influence sphere of the Moon can be considered as a perturbed two body problem around the Moon, while the Lunar probe is near

L. Liu; W. Zhang

2007-01-01

48

Mars Exploration Rovers orbit determination filter strategy

NASA Technical Reports Server (NTRS)

The successful delivery of the Mars Exploration Rover (MER) landers to well within the boundaries of their surface target areas in January of 2004 was the culmination of years of orbit determination analysis. The process began with a careful consideration of the filter parameters used for pre-launch covariance studies, and continued with the refinement of the filter after launch based on operational experience. At the same time, tools were developed to run a plethora of variations around the nominal filter and analyze the results in ways that had never been previously attempted for an interplanetary mission. In addition to achieving sub-kilometer Mars-relative orbit determination knowledge, the filter strategy and process detected unexpected error sources, while at the same time proving robust by indicating thecorrect solution. Consequently, MER orbit determination set a new standard for interplanetary navigation.

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

2004-01-01

49

Mars Exploration Rovers orbit determination filter strategy

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

50

New determination of the orbit of Miranda

NASA Astrophysics Data System (ADS)

Determinations of the orbital elements of Miranda, the innermost satellite of Uranus, which were made subsequent to the determinations of Whitaker and Greenberg (1973) are reported. The present determination is based on observations made during the 1975 and 1977 oppositions with the 155-cm astrometric reflector at Flagstaff Observatory, and during the successive oppositions of 1977, 1978 and 1979 with the Pic-du-Midi 1-m reflector. Comparison of the observed position angles with those predicted from the orbit of Whitaker and Greenberg reveals a discrepancy increasing with time until 1978, indicating the need for an orbital revision. Calculations of a sinusoidal approximation of the residuals in longitude observed in 1948-49 and since 1972 results in a period close to the circulation period of near commensurability between Ariel, Umbriel and Miranda, which may also be interpreted as the gravitational effect of Ariel and Umbriel on Miranda. Determinations of the orbit of Miranda taking into account these gravitational perturbations confirm the previously determined irregularities in inclination and eccentricity. A mass product of Ariel and Umbriel of 1.10 plus or minus 0.25 x 10 to the -10th is also derived. It is noted that observations are continuing to improve the accuracy of the present results.

Veillet, C.

1981-05-01

51

NASA Technical Reports Server (NTRS)

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

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

1990-01-01

52

CHAMP Orbit Determination and Gravity Field Recovery

NASA Astrophysics Data System (ADS)

This paper presents results from precise orbit determination of CHAMP as computed from a reduced dynamic procedure within the GIPSY/OASIS software. Results will be given of the orbital strategy and the tuning procedure for the kinematic stochastic accelerations. The accuracy of the orbits will be quantified by overlap residuals, by comparison against independent orbits submitted to the IGS LEO Pilot Project, and by use of the available tracking data. GPS derived Cartesian positioning is then used as tracking data to recover scaling factors and offsets for the accelerometer data, thruster mismatch and misalignment, and gravity field harmonics. In particular, a comparison will be undertaken of surface forces as inferred from the accelerometer data and from modelling. Selected sets of CHAMP positioning and accelerometer data are subsequently used to derive a CHAMP only gravity field model. Precise orbit determination of geodetic and altimetric satellites will be used to compare the CHAMP only model against existing models and those derived from CHAMP in combination with other satellite data.

Moore, P.; Turner, J.; Qiang, Z.

53

Simulation of Precise Offline Satellite Orbit Determination

In this paper we have taken advantages of precise orbit determination of satellite trajectories using offline simulations. Furthermore perturbation forces which make complex motion equations of satellites and cause more complicated satellites trajectories are simulated using Poisson and Lagrange brackets methods. Moreover perturbation forces effects in the satellites motion are investigated and precise position of satellite is estimated. Finally a

Mohammad Bagher Alaee; Hossein Rahmani

2010-01-01

54

Filtering theory applied to orbit determination

NASA Technical Reports Server (NTRS)

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

Torroglosa, V.

1973-01-01

55

Topex orbit determination using GPS tracking system

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

Hyung Jin Rim

1992-01-01

56

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

57

Kinematic Precise Orbit Determination for Gravity Field Determination

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

D. Švehla; M. Rothacher

58

Formation Flying In Highly Elliptical Orbits Initializing the Formation

NASA Technical Reports Server (NTRS)

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

Mailhe, Laurie; Schiff, Conrad; Hughes, Steven

2000-01-01

59

Topex orbit determination using GPS tracking system

NASA Astrophysics Data System (ADS)

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

Rim, Hyung Jin

60

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

61

On the atmospheric drag in orbit determination for low Earth orbit

NASA Astrophysics Data System (ADS)

The atmosphere model is always a major limitation for low Earth orbit (LEO) in orbit prediction and determination. The accelerometer can work around the non-gravitational perturbations in orbit determination, but it helps little to improve the atmosphere model or to predict the orbit. For certain satellites, there may be some specific software to handle the orbit problem. This solution can improve the orbit accuracy for both prediction and determination, yet it always contains empirical terms and is exclusive for certain satellites. This report introduces a simple way to handle the atmosphere drag for LEO, which does not depend on instantaneous atmosphere conditions and improves accuracy of predicted orbit. This approach, which is based on mean atmospheric density, is supported by two reasons. One is that although instantaneous atmospheric density is very complicated with time and height, the major pattern is determined by the exponential variation caused by hydrostatic equilibrium and periodic variation caused by solar radiation. The mean density can include the major variations while neglect other minor details. The other reason is that the predicted orbit is mathematically the result from integral and the really determinant factor is the mean density instead of instantaneous density for every time and spot. Using the mean atmospheric density, which is mainly determined by F10.7 solar flux and geomagnetic index, can be combined into an overall parameter B^{*} = C_{D}(S/m)?_{p_{0}}. The combined parameter contains several less accurate parameters and can be corrected during orbit determination. This approach has been confirmed in various LEO computations and an example is given below using Tiangong-1 spacecraft. Precise orbit determination (POD) is done using one-day GPS positioning data without any accurate a-priori knowledge on spacecraft or atmosphere conditions. Using the corrected initial state vector of the spacecraft and the parameter B^* from POD, the orbit is propagated to the end of the 11th day (including the first day for POD). It is found that this approach provides reasonable results that match the analytical accuracy. At the end of the 11th day, the along-track error increases to 20km following an approximate time-square law, while the radial error a few hundred meters, the normal error below 50 meters and both follow a mild linear law. The results show that with accurate observation, the mean atmospheric density processed with appropriate approach is sufficient to provide reasonably precise orbit in prediction and determination without having to acquire accurate atmosphere conditions. Once long arc becomes available, the parameter B^* can also be used to study its long-term variation (monthly or seasonal). This can be expected as an alternative way to improve orbit accuracy in prediction and determination for LEO.

Tang, Jingshi; Liu, Lin; Miao, Manqian

2012-07-01

62

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

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

2004-01-01

63

Characteristic initial data for a star orbiting a black hole

NASA Astrophysics Data System (ADS)

We take further steps in the development of the characteristic approach to enable handling the physical problem of a compact self-gravitating object, such as a neutron star, in close orbit around a black hole. We examine different options for setting the initial data for this problem and, in order to shed light on their physical relevance, we carry out short time evolution of this data. To this end we express the matter part of the characteristic gravity code so that the hydrodynamics are in conservation form. The resulting gravity plus matter relativity code provides a starting point for more refined future efforts at longer term evolution. In the present work we find that, independently of the details of the initial gravitational data, the system quickly flushes out spurious gravitational radiation and relaxes to a quasiequilibrium state with an approximate helical symmetry corresponding to the circular orbit of the star.

Bishop, Nigel T.; Gómez, Roberto; Lehner, Luis; Maharaj, Manoj; Winicour, Jeffrey

2005-07-01

64

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.

65

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

66

Mars Exploration Rover Cruise Orbit Determination

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

67

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

68

Topocentric orbit determination: Algorithms for the next generation surveys

The process of calculating a good orbit from astrometric observations of the same object involves three main steps: preliminary orbit determination, least squares orbit fitting, and quality control assessing the orbit's uncertainty and reliability. For the next generation sky surveys, with much larger number density of observations, new algorithms, or at least substantial revisions of the classical ones, are needed.

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

2008-01-01

69

ERS-1 and ERS-2 operational and precise orbit determination

This paper presents the European Space Operations Centre's orbit determination and prediction systems for the ERS-1 mission. The routine operational orbit determination and prediction subsystem is discussed briefly, and statistics of the accuracy compared to the requirements are given. The precise orbit determination subsystem is then described, and the accuracy of its results are compared to those of the operational

R. Zandbergen; J. M. Dow; M. Romay Merino; R. Píriz

1995-01-01

70

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

71

EURECA 11 months in orbit: Initial post flight investigation results

NASA Technical Reports Server (NTRS)

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

Dover, Alan; Aceti, Roberto; Drolshagen, Gerhard

1995-01-01

72

Orbit determination for the next generation asteroid\\/comet surveys

The classical methods of orbit determination cannot cope with the data flow expected from the next generation surveys. The main problem is that the detections of each object within one night do not define an orbit, but only contain information to estimate a four parameters attributable, containing two angles and two angular rates. Orbit determination requires the identification of two

A. Milani

2005-01-01

73

Reduced-Dynamic Technique for Precise Orbit Determination.

National Technical Information Service (NTIS)

Observations of the Global Positioning System (GPS) will enable a reduced-dynamic technique for achieving subdecimeter orbit determination of earth-orbiting satellites. With this technique, information on the transition between satellite states at differe...

S. C. Wu T. P. Yunck C. L. Thornton

1990-01-01

74

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

75

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

76

Determination of libration amplitudes from orbit

NASA Astrophysics Data System (ADS)

Mercury's internal structure is the most puzzling among the terrestrial planets. The space missions MESSENGER and BepiColombo will play an important role in constraining the structure, formation, and evolution of Mercury. In particular, in Peale's experiment, insight into Mercury's deep interior will be obtained from observations of the 88-day forced libration, the obliquity, and the degree-two coefficients of the gravity field of Mercury. Of those quantities, the libration is the most difficult to measure and will hence be the limiting factor.. We report here on aspects of the observational strategy to determine the libration amplitude.. Repeated photographic measurements of selected target positions on the surface of Mercury are central to the strategy to determine the libration in the frame of the Bepi-Colombo mission. We simulated these measurements in order to estimate the accuracy of the reconstruction of the rotational motion of the planet, as a function of the quantity of measurements made, the number of different targets considered and their locations on the surface of the planet. From this study, we determine criteria for the distribution and number of target positions to maximize the accuracy on the rotation determination, from which the libration is extracted. We also assess the possibility to measure the Galilean satellites' libration from orbit through the same technique used for Mercury. Such measurements would, as for Mercury, deliver crucial information on the satellites' inner structure, in particular on expected subsurface oceans, and it would be of interest to integrate the required instruments in a future mission.

Pfyffer, G.; Rambaux, N.; Rivoldini, A.; van Hoolst, T.; Dehant, V.

77

Dynamic orbit determination using GPS measurements from TOPEX/POSEIDON

NASA Technical Reports Server (NTRS)

The GPAS data acquired by the TOPEX/POSEIDON (T/P) Demonstration Receiver (DR) have been used in a dynamic orbit determination, which was based on the description of the gravitational and nongravitational forces in the equations of motion. The GPS carrier phase data were processed in a double difference mode to remove clock errors, including the effects of Selective Availability. Simultaneous estimation of the T/P orbit and GPS orbits was performed using five 10-day cycles in the interval between December (1992) and April (1993). The resulting T/P orbits have been compared with the orbits determined from Satellite Laser Ranging, the French one-way Doppler tracking system, DORIS, and with the JPL reduced dynamic orbit determination strategies and force models with the GPS/DR to those used with SLR/DORIS, the radial component of the T/P orbit (based on JGM-2) was found to agree better than 30 mm (rms) and 35 mm with the JPL reduced dynamic orbit. An experiment gravity tuning was accomplished using four cycles of GPS/DR data. The resulting GPS./DR-orbits, determined by the dynamic technique with the experimental gravity field, are in better agreement with the JPL reduced dynamic orbits in both the radial component (21-25 mm) and altimeter crossover residuals than the JGM-2 orbits. (21-25 mm) and altimeter crossover residuals than the JGM-2 orbits.

Schultz, B. E.; Tapley, B. D.; Abusali, P. A. M.; Rim, H. J.

1994-01-01

78

An Efficient LEO Precision Orbit Determination For GPS Meteorology

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

T. Bae; D. Grejner-Brzezinska

2006-01-01

79

Comparison of four European orbit determination systems

The objective of this paper is to present the activities and the main conclusions of the IOI (In-Orbit Infrastructure) Flight Dynamics Working Group. This IOIFDWG is an inter-agency working group composed of flight dynamics experts coming from the following space agencies: ASI, DLR, ESA and CNES. These agencies are in charge of elements of the future European orbital infrastructure such

F. Alby; G. Bianco; J. Fourcade; E. Gill; M. Kirschner; V. Luceri; R. Mesnard; O. Montenbruck; M. Schneller; J. Schoemaekers

1994-01-01

80

Ulysses orbit determination at high declinations

NASA Technical Reports Server (NTRS)

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

Mcelrath, Timothy P.; Lewis, George D.

1995-01-01

81

Spacecraft Orbit Determination with The B-spline Approximation Method

NASA Astrophysics Data System (ADS)

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

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

2014-04-01

82

Jason-2 Precise Orbit Determination : current status and future improvements

NASA Astrophysics Data System (ADS)

The JASON-2 satellite was launched on June 20, 2008 to continue the series of spaceborne radar altimeter missions initiated with TOPEX-POESEIDON in 1992 and continued by its follow-on, JASON-1, starting in 2002. From the very beginning, Precise Orbit Determination (POD) has been a key component of the success of these satellite altimeter missions. In order to meet the 1.5 cm radial accuracy required for the operational precise orbits included in the Geophysical Data Record (GDR), both JASON satellites are equipped with three state-of-the-art track-ing systems: Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) , Satellite Laser Ranging (SLR), and Global Positioning System (GPS). Over the past 10 years, several improvements in the quality as well as in the spatial and the temporal coverage of these tracking data, together with the enhancements in models and parameterization techniques, have made it possible to achieve the "1-cm" goal. Today, JASON-2 orbits computed by various research groups compare at the sub-centimeter level in terms of radial RMS over a few days. A significant effort is now committed toward reducing the latency of the precise orbit products while maintaining a high level of accuracy and operational robustness. Most important, as the altimeter data set now spans over almost two decades, scientists are able to reveal small climate signals such as a 3mm/year rise of the global Mean Sea Level (MSL) as well as interannual fluctuations of few mm amplitude. To maintain this level of performance, new requirements on the long term drifts of all components of the measurement system of future altimeter missions are needed. In this context, the stability of the radial orbit error properties over several years is increasingly important. Typically, global RMS values can cover systematic variations that have a particular spatial and temporal coherence, and which are of particular interest for the altimeter data analysts. In particular, errors in the DORIS, SLR and GPS realizations of the terrestrial reference system in which orbit solutions are computed, mismodeled surface forces and temporal variations of the gravity field are fundamental contributors to the orbit error budget at the global and local scales. Two years after launch, this talk addresses these topics with an overview of JASON-2 POD performance, both in term of short term and long term accuracy, outlining past progress and prospects for future improvements.

Cerri, Luca

83

Two Line Element Aided Orbit Determination Using Single Station SLR Data

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

84

NASA Astrophysics Data System (ADS)

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

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

2004-09-01

85

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

86

Multiprocessor implementation of algorithms for multisatellite orbit determination

NASA Astrophysics Data System (ADS)

Previous studies of parallel processing methods for use with satellite related, many parameter estimation problems indicate the need for faster numerical integration methods. Parallel numerical integration methods for use in satellite orbit determination were studied and tested. Several methods such as parallel Runge-Kutta schemes showed improvement over serial methods when tested on the two body problem. Existing orbit determination routines were modified for use on a Cray T3E parallel supercomputer. These routines were used to test a selected set of the parallel integration routines, including Parallel Extrapolation and Parallel Iterated Runge-Kutta methods, for the case of the GPS satellite constellation orbits with nominal force models. None of the methods showed significant improvement over the fastest serial method, a Class II predictor-corrector scheme. A combined parallel observation processing and parallel least squares orbit determination program was compared to a serial orbit determination program. The fastest parallel orbit determination scheme, a 16 processor version, was not superior to the fastest time of the serial orbit determination scheme, but was just as fast as the average time of the serial scheme. Use of the fastest serial integration method in the parallel scheme revealed that the numerical integration contributed almost one quarter of the fastest overall processing time. The primary hindrance to the performance of the parallel scheme was caused by delays associated with synchronization of the processors. Improved force model algorithms for use in GPS orbit determination were implemented. Pseudo-stochastic velocity changes and the updated solar radiation pressure model developed by the CODE Analysis Center of the IGS were tested using 30 hour and 3 day orbit arc lengths. Use of these models resulted in an improvement of the orbit overlap statistics but a degradation of the differences of the orbits with respect to IGS orbits.

Nagel, Peter Borden

1999-11-01

87

Evaluation of Improved Spacecraft Models for GLONASS Orbit Determination

High-fidelity spacecraft models become more important as orbit determination strategies achieve greater levels of precision and accuracy. In this presentation, we assess the impacts of new solar radiation pressure and attitude models on precise orbit determination (POD) for GLONASS spacecraft within JPLs GIPSY-OASIS software. A new solar radiation pressure model is developed by empirically fitting a Fourier expansion to solar

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

2010-01-01

88

Multiprocessor implementation of algorithms for multisatellite orbit determination

Previous studies of parallel processing methods for use with satellite related, many parameter estimation problems indicate the need for faster numerical integration methods. Parallel numerical integration methods for use in satellite orbit determination were studied and tested. Several methods such as parallel Runge-Kutta schemes showed improvement over serial methods when tested on the two body problem. Existing orbit determination routines

Peter Borden Nagel

1999-01-01

89

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

90

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

91

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

92

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

93

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

94

CHAMP precise orbit determination using GPS data

At 15 July 2000 the Challenging Minisatellite Payload (CHAMP) was launched into a near polar orbit around the earth at an altitude of approximately 450 km. The primary scientific objectives of the mission include the precise measurement of the earth's gravity and magnetic fields and the high resolution profiling of the atmosphere and ionosphere. In order to reach these mission

J. van den Ijssel; P. Visser

2002-01-01

95

GPS as an orbit determination subsystems

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

Richard Fennessey; Pat Roberts; Robin Knight; Bart Vanvolkinburg

1995-01-01

96

Orbit Determination of the Orbital Reentry Experiment (OREX) Vehicle by GPS.

National Technical Information Service (NTIS)

A Japanese first spaceborne GPS receiver, within the Orbital Reentry Experiment (OREX) vehicle, was lanuched by the H-II launch vehicle on February 4, 1994. The observed GPS data are analyzed in this report to evaluate the accuracy of orbit determination ...

M. Harigae M. Murata T. Tsujii H. Shingu H. Tomita S. Matsumoto

1995-01-01

97

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 model of lunar topography yet produced. These altimetric observations have been used to improve the lunar geodetic grid to ?10 m radial and ?100 m spatial accuracy

David E. Smith; Maria T. Zuber; Gregory A. Neumann; Frank G. Lemoine; Erwan Mazarico; Mark H. Torrence; Jan F. McGarry; David D. Rowlands; James W. Head; Thomas H. Duxbury; Oded Aharonson; Paul G. Lucey; Mark S. Robinson; Olivier S. Barnouin; John F. Cavanaugh; Xiaoli Sun; Peter Liiva; Dan-dan Mao; James C. Smith; Arlin E. Bartels

2010-01-01

98

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

99

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

100

NASA Astrophysics Data System (ADS)

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

Tukaram Aghav, Sandip; Achyut Gangal, Shashikala

2014-06-01

101

Precision orbit determination for the TOPEX/Poseidon mission

NASA Technical Reports Server (NTRS)

Computation of precise orbits for the TOPEX/Poseidon (T/P) spacecraft is analyzed focusing on gravity field modeling, nonconservative force modeling, satellite tracking technologies, and orbit determination software. It was found that the radial orbit error budget for T/P allows 10 cm rms error due to gravity field mismodeling, 3 cm due to solid earth and ocean tides, and 6 cm due to radiative forces, and 3 cm due to atmospheric drag. It is concluded that the current models are capable of achieving the radial orbit error requirements.

Nerem, R. S.; Marshall, J. A.; Putney, B. H.; Pavlis, E. C.; Klosko, S. M.; Williamson, R. G.; Zelensky, N. P.

1992-01-01

102

Precise Orbit Determination for the GOCE Satellite Using GPS

NASA Astrophysics Data System (ADS)

Apart from the gradiometer as the core instrument the first ESA Earth Explorer Core mission GOCE Gravity field and steady-state Ocean Circulation Explorer carries a 12-channel GPS receiver dedicated for precise orbit determination POD of the satellite The EGG-C European GOCE Gravity-Consortium led by the Technical University in Munich is building the GOCE HPF High-level Processing Facility dedicated to the Level 1b to Level 2 data processing One of the tasks of this facility is the computation of the Precise Science Orbit PSO for GOCE The PSO includes a reduced-dynamic and a kinematic orbit solution The baseline for the PSO is a zero difference procedure using GPS satellite orbits clocks and Earth Rotation Parameters ERPs from CODE Center for Orbit Determination in Europe one of the IGS International GNSS Service Analysis Centers The scheme for reduced-dynamic and kinematic orbit determination is based on experiences gained from CHAMP and GRACE POD and is realized in one processing flow Particular emphasis is put on maximum consistency in the analysis of day-boundary overlapping orbital arcs as well as on the higher data sampling rate and on differences originating from different GPS antenna configuration We focus on the description of the procedure used for the two different orbit determinations and on the validation of the procedure using real data from the two GRACE satellites as well as simulated GOCE data

Bock, H.; Jäggi, A.; Svehla, D.; Beutler, G.; Hugentobler, U.; Visser, P.

103

GOES orbit and attitude determination: theory, implementation, and recent results

This paper presents the mathematical formulation and implementation techniques used in the GOES orbit and attitude determination (OAD) software. Also presented are some recent results obtained by analyzing data from the operational GOES. The OAD software, a key component of the orbit and attitude tracking subsystems, has been in use for operating the GOES spacecraft successfully since the beginning. Three

Kwok M. Ong; Steven D. Lutz

1996-01-01

104

Autonomous orbit determination for future GEO and HEO missions

The use of GNSS space receivers for autonomous orbit determination is receiving increasing interest due to the important economical and operational benefits made possible by the reduced on-ground operations and the improved pointing performance when associated to one Star Tracker. However, the exploitation of GNSS for navigating satellites in orbits beyond the GNSS constellations has not yet gained full acceptance

José F. M. Lorga; Pedro F. Silva; Fabio Dovis; Andrea Di Cintio; Steeve Kowaltschek; David Jimenez; Roger Jansson

2010-01-01

105

Orbit determination strategy using single-frequency GPS data

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

Yoola Hwang

2003-01-01

106

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

NASA Astrophysics Data System (ADS)

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

Jianguo, Yan; Jingsong, Ping; Fei, Li

107

Status of Precise Orbit Determination for Jason-2 Using GPS

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

108

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

109

Determination of the orbital parameters of binary pulsars

NASA Astrophysics Data System (ADS)

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

Bhattacharyya, Bhaswati; Nityananda, Rajaram

2008-06-01

110

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

111

NASA Astrophysics Data System (ADS)

Between the years 2004 and 2005 the launch of the first gradiometric satellite is planned. This satellite will be an important element of the Gravity Field and Steady - State Ocean Circulation Explorer Mission (GOCE). This mission is one of the reasons for performing the simulation research of the Satellite Gravity Gradiometry. Our work contains the theory description and simulation results of the satellite orbit determination using the gravity tensor observations. In the process of the satellite orbit determination the initial dynamic state vector corrections are obtained. These corrections are estimated by means of the gravity gradiometry measurements. The performed simulations confirm the possibility of satellite orbit determination by means of the gravity tensor observations.Key words. satellite geodesy, satellite gradiometry, satellite orbits

Boboj?, A.; Dro?yner, A.

2003-06-01

112

Evaluation of Improved Spacecraft Models for GLONASS Orbit Determination

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

113

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

114

Expected orbit determination performance for the TOPEX/Poseidon mission

NASA Technical Reports Server (NTRS)

Each of the components required for the computation of precise orbits for the TOPEX/Poseidon (T/P) spacecraft - gravity field modeling, nonconservative force modeling, and satellite tracking technologies - is examined. The research conducted in the Space Geodesy Branch at Goddard Space Flight Center in preparation for meeting the 13-cm radial orbit accuracy requirement for the T/P mission is outlined. New developments in modeling the earth's gravitational field and modeling the complex nonconservative forces acting on T/P are highlighted. The T/P error budget is reviewed, and a prelaunch assessment of the predicted orbit determination accuracies is summarized.

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

1993-01-01

115

GPS single-frequency orbit determination for low Earth orbiting satellites

NASA Astrophysics Data System (ADS)

The determination of high-precision orbits for Low Earth Orbiting (LEO) satellites (e.g., CHAMP, GRACE, MetOp) is based on dual-frequency tracking data from onboard GPS receivers. The two frequencies allow it to eliminate the first order ionosphere effects on the level of the carrier phase measurement noise. Data screening and precise orbit determination (POD) procedures are optimized under the assumption of the availability of two frequencies. If only single-frequency data are available, the algorithms have to be modified to consider the ionospheric effect. We develop and study different approaches for POD with single-frequency data. Reduced-dynamic as well as kinematic POD techniques are considered. The potential of single-frequency POD in different environments is assessed by comparing the results with dual-frequency POD for LEOs orbiting at different orbital heights. Moreover, the impact of different data sampling rates on single-frequency POD is considered. Our study helps to define requirements for GPS receivers and POD algorithms for future LEO missions for which only moderate orbit accuracy is needed.

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

116

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

117

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

118

Orbit determination error analyses for POPSAT and ERS-1

The missions of both the future ESA geodetic POPSAT and remote-sensing ERS-1 satellites require that the orbits are known very accurately. This paper summarizes some results of POPSAT and ERS-1 orbit determination error analyses for 1-5 day arcs of tracking data acquired by global tracking networks, and of error analyses to estimate the accuracy with which the positions of ground

K. F. Wakker; B. A. C. Ambrosius

1985-01-01

119

ERS ORBIT DETERMINATION AND GRAVITY FIELD MODEL TAILORING: RECENT DEVELOPMENTS

In the last ten years significant advances have been made in gravity field modelling, culminating in general-purpose models like JGM-3, TEG-3 and EGM96. Significant defects remain in the quality of the models when applied to orbit determination of some altimeter satellites, leading to large orbit errors, characterised by the geographically-correlated nature of the altimeter crossover height difference. However, we have

Remko Scharroo; Pieter Visser; Neil Peacock

120

Orbital Tumour as Initial Manifestation of Acute Myeloid Leukemia: Granulocytic Sarcoma: Case Report

We report orbital involvement as an initial manifestation of acute myeloid leukemia in a 57-year-old woman. The patient presented\\u000a with painful proptosis and limited ocular motility. Orbital computed tomography revealed bilateral homogeneous masses. Orbital\\u000a biopsy was performed on the right side; and histopathology disclosed a myelocytic tumour. Despite treatment using irradiation\\u000a and chemotherapy, the patient died eleven months after presentation.

Erika Maka; Olga Lukáts; Jeannette Tóth; Sándor Fekete

2008-01-01

121

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

122

From Ancient Paradoxes to Modern Orbit Determination

In the 5th century BC, Zeno advanced a set of paradoxes to show motion and time are impossible, hence an illusion. The problem of motion has since driven much scientific thought and discovery, extending to Einstein's insights and the quantum revolution. To determine and predict the motion of remote objects within the solar system, a methodology has been refined over

Jon D. Giorgini

2008-01-01

123

Orbit Determination Using GPS Navigation Solution

The Global Positioning System (GPS) is a satellite navigation system that allows the users to determine position, velocity and the time with high precision. Its main purposes are aid to radionavigation in three dimensions with high precision positioning, navigation in real time, global coverage and quick acquisition of data sent by the GPS satellites. The purpose of this work is

V. M. Gomes; H. K. Kuga; A. P. Chiaradia; A. F. Prado

2004-01-01

124

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

125

Application of GPS tracking techniques to orbit determination for TDRS

NASA Technical Reports Server (NTRS)

In this paper, we evaluate two fundamentally different approaches to TDRS orbit determination utilizing Global Positioning System (GPS) technology and GPS-related techniques. In the first, a GPS flight receiver is deployed on the TDRSS spacecraft. The TDRS ephemerides are determined using direct ranging to the GPS spacecraft, and no ground network is required. In the second approach, the TDRSS spacecraft broadcast a suitable beacon signal, permitting the simultaneous tracking of GPS and TDRSS satellites from a small ground network. Both strategies can be designed to meet future operational requirements for TDRS-2 orbit determination.

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

1993-01-01

126

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

127

20 CFR 320.5 - Initial determinations.

Code of Federal Regulations, 2010 CFR

...RAILROAD UNEMPLOYMENT INSURANCE ACT INITIAL DETERMINATIONS UNDER THE RAILROAD UNEMPLOYMENT INSURANCE ACT AND REVIEWS OF...respect to each claim for unemployment or sickness...Policy and Systems shall issue instructions...

2010-04-01

128

20 CFR 320.5 - Initial determinations.

Code of Federal Regulations, 2010 CFR

...RAILROAD UNEMPLOYMENT INSURANCE ACT INITIAL DETERMINATIONS UNDER THE RAILROAD UNEMPLOYMENT INSURANCE ACT AND REVIEWS OF...respect to each claim for unemployment or sickness...Policy and Systems shall issue instructions...

2009-04-01

129

Topocentric orbit determination: Algorithms for the next generation surveys

NASA Astrophysics Data System (ADS)

The process of calculating a good orbit from astrometric observations of the same object involves three main steps: preliminary orbit determination, least squares orbit fitting, and quality control assessing the orbit's uncertainty and reliability. For the next generation sky surveys, with much larger number density of observations, new algorithms, or at least substantial revisions of the classical ones, are needed. The classical theory of preliminary orbit algorithms was incomplete in that the consequences of the topocentric correction had not been fully studied. We show that it is possible to rigorously account for topocentric observations and that this correction may increase the number of alternate preliminary orbits without impairing the overall performance. We have developed modified least squares algorithms including the capability of fitting the orbit to a reduced number of parameters. The restricted fitting techniques can be used to improve the reliability of the orbit computing procedure when the observed arcs have small curvature. False identification (where observations of different objects are incorrectly linked together) can be discarded with a quality control on the residuals and a 'normalization' procedure removing duplications and contradictions. We have tested our algorithms on two simulations based on the expected performance of Pan-STARRS—one of the next generation all-sky surveys. The results confirm that large sets of discoveries can be handled very efficiently resulting in good quality orbits. In these tests we lost only 0.6 to 1.3% of the possible objects, with a false identification rate in the range 0.02 to 0.06%.

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

2008-05-01

130

A comparison of nonlinear filters for orbit determination

NASA Astrophysics Data System (ADS)

The orbit determination accuracy and efficiency of two recursive filters, an iterated-extended Kalman filter (EKF) and a Gaussian second-order filter are compared to that of a batch least squares filter. Actual observation data for satellites in three different types of orbits are used. Following the approach of Tapley and Choe (1972), the effect of the second-order terms in the dynamics, obsevations, and gain are individually evaluated. The efficiency of the filters, expressed as computer time of operation and required storage, are compared. It is concluded that the state vector estimate from the Gauss filter provides the best estimate for propagating the state vector forward in time of a satellite with high altitude and noncircular orbit and for a satellite with a low altitude and a noncircular orbit. The EKF filter is much faster than the other two types.

Boden, D. G.; Conway, B. A.

1986-08-01

131

Precise GPS orbit determination results from 1985 field tests

NASA Technical Reports Server (NTRS)

Data from three different receiver types have been used to obtain precise orbits for the satellites of the Global Positioning System (GPS). The data were collected during the 1985 March-April GPS experiment to test and validate GPS techniques for precision orbit determination and geodesy. A new software package developed at the Jet Propulsion Laboratory (JPL), GIPSY (GPS Inferred Positioning SYstem), was used to process the data. To assess orbit accuracy, solutions are compared using integrated doppler data from various different receiver types, different fiducial sites, and independent data arcs, including one spanning six days. From these intercomparisons, orbit accuracy for a well-tracked GPS satellite of three meters in altitude and about five meters in each of down and cross-track components are inferred.

Lichten, S. M.; Border, J. S.; Wu, S.-C.; Williams, B. G.; Yunck, T. P.

1986-01-01

132

Orbit determination for the Voyager II Uranus encounter

NASA Technical Reports Server (NTRS)

The Voyager II flyby of Uranus in January 1986 was the most distant planetary encounter ever attempted, and presented unique challenges to the process of orbit determination. Long light-times and spacecraft receiver difficulties hampered the collection of two-way radiometric data and helped bring about the maturation of a Very Long Baseline Interferometry navigational data type during the long cruise from Saturn. Planet and satellite ephemeris uncertainties necessitated the use of the onboard spacecraft optical system for Uranus-relative navigation. During the close approach phase, these optical data were combined with radiometric data to drive the Uranus system-relative uncertainties down to the level of a few tens of kilometers. This paper contains qualitative and quantitative results and conclusions based on orbit determination experience during Uranus cruise and encounter. Topics include an overview of the navigation-related mission events and requirements, and a review of the salient orbit determination results.

Taylor, T. H.; Jacobson, R. A.; Synnott, S. P.; Lewis, G. D.; Riedel, J. E.

1986-01-01

133

Interplanetary orbit determination. [for Viking 1 and 2 spacecraft

NASA Technical Reports Server (NTRS)

A general description of the Viking interplanetary orbit determination activity extending from launch to Mars encounter is given. The emphasis is on the technical fundamentals of the problem, basic strategies and data types used, quantitative results, and specific conclusions derived from the inflight experience. Special attention is given to the use of the spacecraft-based optical measurements and their first application as a principal navigational data type for an interplanetary mission. The optical-based orbit determination, in fact, was the primary contributor to the exceptional interplanetary navigation accuracy experienced by both Viking missions. The Viking application of optical orbit determination relied in large part on the technology developed and demonstrated by the Mariner 9 Optical Navigation Demonstration.

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

1979-01-01

134

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

NASA Technical Reports Server (NTRS)

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

Ulvestad, J. S.

1992-01-01

135

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

136

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

137

Evaluation of advanced geopotential models for operational orbit determination

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

138

Orbit Determination for Mars Global Surveyor During Mapping

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

139

GPS single-frequency orbit determination for low Earth orbiting satellites

NASA Astrophysics Data System (ADS)

The determination of high-precision orbits for Low Earth Orbiting (LEO) satellites (e.g., CHAMP, GRACE, MetOp-A) is based on dual-frequency tracking data from on-board GPS (Global Positioning System) receivers. The two frequencies allow it to eliminate the first order ionosphere effects. Data screening and precise orbit determination (POD) procedures are optimized under the assumption of the availability of two frequencies. If only single-frequency data is available, the algorithms have to be modified to consider the ionospheric effect. We develop and study different approaches for POD with single-frequency data. Reduced-dynamic as well as kinematic POD techniques using pseudorange and carrier phase GPS data are considered. One week of data in the year 2007 is used to assess the potential of single-frequency POD in different environments by comparing the results with dual-frequency POD for LEOs orbiting the Earth in different heights. Data from the two GRACE and the MetOp-A satellites is processed for this purpose. Moreover, the impact of different data sampling rates on single-frequency POD is considered. For this period with low solar activity a 3D orbit accuracy of 1 dm could be reached for one of the GRACE satellites. It could be shown that it is necessary to have a high data sampling of 10 s or more available when the impact of the ionosphere is high due to low altitude of the satellite or high solar activity. Our study helps to define requirements for GNSS (Global Navigation Satellite System) receivers and POD algorithms for future LEO missions for which only moderate orbit accuracy of about one to few decimeter is needed.

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

2009-03-01

140

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

141

Orbit determination of Sakigake and Suisei encountering Halley's Comet

The orbit determination program used to track the Japanese Halley's comet flyby satellites is described. A square root filter form is adopted in addition to the normal-equation form as the estimation formula, since filtering itself has numerical difficulty because of poor observability due to the long distance between the probe and the tracking station. The effect of general relativity is

T. Nishimura; T. Takano; T. Yamada; T. Kato; T. Jano; T. Wakaki; T. Mikami; A. Ushikoshi; N. Mizutani

1986-01-01

142

Reduced dynamic orbit determination using GPS code and carrier measurements

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

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

2005-01-01

143

Simplified Solution to Determination of a Binary Orbit

NASA Astrophysics Data System (ADS)

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

Asada, H.; Akasaka, T.; Kudoh, K.

2007-04-01

144

Numerical comparison of Kalman filter algorithms - Orbit determination case study

Numerical characteristics of various Kalman filter algorithms are illustrated with a realistic orbit determination study. The case study of this paper highlights the numerical deficiencies of the conventional and stabilized Kalman algorithms. Computational errors associated with these algorithms are found to be so large as to obscure important mismodeling effects and thus cause misleading estimates of filter accuracy. The positive

G. J. Bierman; C. L. Thornton

1977-01-01

145

Nominal ocean tide models for TOPEX precise orbit determination

The increasing accuracy of satellite laser tracking systems and the stringent requirements on the radial error budget of the TOPEX\\/Poseidon mission put severe demands on the force model used for orbit determination. The ocean tide component of the force model is addressed in order to establish a nominal tide model that meets the requirement of 2 cm RMS perturbation amplitude

Stefano Casotto

1989-01-01

146

Accuracy of orbit determination from ionospherically corrupted tracking data

Description of a procedure for correcting the adverse effects of ionospheric tracking-data corruption upon the accuracy of satellite orbit determinations based on these data. Under the proposed procedure, the ionosphere is modeled by a single parameter whose statistical distribution is approximately normal. This parameter is then included in the solution vector, along with the satellite position and velocity. The procedure

P. Norris

1974-01-01

147

Statistical method for the determination of asteroid and satellite orbits

The paper describes a Kalman-Bucy filtering technique of orbit determination. The principle of the method is to compare at every instant the calculated and observed position of a celestial body, taking into account observational errors. The two quantities are considered as two independent measurements of one physical quantity. From these two values a third, more precise value is deduced. The

R. Dvorak; C. Edelman

1979-01-01

148

Dynamical model compensation for near-earth satellite orbit determination

Operational requirements in modern space applications often demand orbit determination accuracies which are limited by fundamental mathematical and computational restrictions. It is shown in realistic computer simulation studies how these difficulties can be alleviated for typical near-earth satellites by employing dynamical model compensation (DMC) and accurate observations in the extended Kalman filter. Unmodeled and unknown accelerations affecting the motion of

K. A. Myers; B. D. Tapley

1975-01-01

149

Precise orbit determination of SPOT platform with DORIS

DORIS (Doppler Orbitography and Radiopositioning Integrated by Satellite) is a new precise orbit determination system developed by CNES to meet the high accuracy requirement of oceanographic altimetric missions of TOPEX\\/Poseidon. The system is based upon a worldwide network of about 50 ground transmitting beacons, a Doppler receiver onboard of the satellite, a ground segment to control the system and a

F. Nouel; J. P. Berthias; P. Broca; M. Deleuze; A. Guitart; P. Laudet; C. Pierret; A. Piuzzi; C. Valorge

1992-01-01

150

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

151

Geos-C Orbit Determination with Satellite to Satellite Tracking.

National Technical Information Service (NTIS)

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 was studied. It is shown that with proper estimation procedures it is possible to obtain fr...

P. Argentiero

1974-01-01

152

A Role for Improved Angular Observations in Geosynchronous Orbit Determination

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

Christopher Andrew Sabol

1998-01-01

153

High precision GPS orbit determination using March 1985 demonstration data

NASA Technical Reports Server (NTRS)

Preliminary orbit determination for satellites in the U.S. Department of Defense's Global Positioning System has been performed using GPS carrier phase data collected in March-April 1985 at 10 sites in the continental United States. The data were analyzed using a new data processing software package called GIPSY (GPS Inferred Positioning SYstem) and with existing covariance analysis software. Data from one day have been processed with average formal position errors of 1.4 to 3.6 meters. The true errors are probably somewhat larger. Covariance results are presented which suggest that the orbits can be obtained with formal errors under 2 meters after certain software issues are resolved.

Bertiger, W.; Wu, S.-C.; Border, J. S.; Lichten, S. M.; Williams, B. G.; Wu, J.-T.

1986-01-01

154

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

155

Expected orbit determination performance for the TOPEX/Poseidon mission

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

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

1993-03-01

156

Demonstration of orbit determination using same-beam interferometry for Magellan and Pioneer 12

NASA Technical Reports Server (NTRS)

Orbit determination results are presented for Magellan and Pioneer 12 utilizing same-beam interferometer (SBI) data, which is a new data type for planetary orbiter navigation. The orbit determination data employing this data type, based on orbit-to-orbit consistency, has been explained in terms of nominal error models. Results show the orbit determination accuracy for Pioneer 12 using Doppler plus SBI data to be better than the accuracy utilizing only Doppler data by 30 percent.

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

1992-01-01

157

Demonstration of orbit determination using same-beam interferometry for Magellan and Pioneer 12

NASA Astrophysics Data System (ADS)

Orbit determination results are presented for Magellan and Pioneer 12 utilizing same-beam interferometer (SBI) data, which is a new data type for planetary orbiter navigation. The orbit determination data employing this data type, based on orbit-to-orbit consistency, has been explained in terms of nominal error models. Results show the orbit determination accuracy for Pioneer 12 using Doppler plus SBI data to be better than the accuracy utilizing only Doppler data by 30 percent.

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

1992-08-01

158

Initial Conditions for an Orbital Resonance in a Satellite System.

National Technical Information Service (NTIS)

This project undertook to examine the conditions of the 3/2 resonance between the planets of Pluto and Neptune and try to determine whether it was possible for Pluto to have escaped from Neptune and became his moon. The writer uses numerical integration a...

S. M. Hopkins

1978-01-01

159

Nonorthogonal molecular orbital method: Single-determinant theory.

Using the variational principle, we have derived a variant of the Adams-Gilbert equation for nonorthogonal orbitals of a single-determinant wave function, which we name the modified Adams-Gilbert equation. If we divide the molecular system into several subsystems, such as bonds, lone pairs, and residues, we can solve the equations for the subsystems one by one. Thus, this procedure has linear scaling. We have presented a practical procedure for solving the equations that is also applicable to macromolecular calculations. The numerical examples show that the procedure yields, with reasonable effort, results comparable with those of the Hartree-Fock-Roothaan method for orthogonal orbitals. To resolve the convergence difficulty in the self-consistent-field iterations, we have found that virtual molecular-orbital shifts are very effective. PMID:24880270

Watanabe, Yoshihiro; Matsuoka, Osamu

2014-05-28

160

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

161

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

162

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

163

NASA Astrophysics Data System (ADS)

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

Lee, Byoung-Sun

2005-09-01

164

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

165

Precise Orbit Determination and Gravity Field Recovery from CHAMP

NASA Astrophysics Data System (ADS)

This paper presents results from precise orbit determination of CHAMP as computed from a reduced dynamic procedure within the GIPSY-OASIS II software. Results will be given of the orbital strategy and the tuning procedure for the kinematic stochastic accelerations. The accuracy of the orbits will be quantified by overlap residuals, by comparison against independent solutions submitted to the IGS LEO Pilot project, and by use of the available SLR tracking data. GPS derived Cartesian positioning is then used as tracking data to recover scaling factors and offsets for the accelerometer data, thruster mismatch and misalignment, and gravity field harmonics. In particular, a comparison will be undertaken of surface forces as inferred from the accelerometer data and from modelling. Selected sets of CHAMP positioning and accelerometer data are subsequently used to derive a CHAMP only gravity field model. Precise orbit determination of geodetic and altimetric satellites will be used to compare the CHAMP only model against existing models and those models derived from CHAMP in combination with other satellite data.

Moore, P.

2002-05-01

166

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

2012-07-01

167

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

168

A reduced-dynamic technique for precise orbit determination

NASA Technical Reports Server (NTRS)

Observations of the Global Positioning System (GPS) will enable a reduced-dynamic technique for achieving subdecimeter orbit determination of earth-orbiting satellites. With this technique, information on the transition between satellite states at different observing times is furnished by both a formal dynamic model and observed satellite positional change (which is inferred kinematically from continuous GPS carrier-phase data). The relative weighting of dynamic and kinematic information can be freely varied. Covariance studies show that in situations where observing geometry is poor and the dynamic model is good, the model dominates determination of the state transition; where the dynamic model is poor and the geometry strong, carrier phase governs the determination of the transition. When neither kinematic nor dynamic information is clearly superior, the reduced-dynamic combination of the two can substantially improve the orbit-determination solution. Guidelines are given here for selecting a near-optimal weighting for the reduced-dynamic solution, and sensitivity of solution accuracy to this weighting is examined.

Wu, S. C.; Yunck, T. P.; Thornton, C. L.

1990-01-01

169

For LEO orbit determination based on Bi-satellite Positioning System (BPS), trajectory error of positioning satellites becomes bottle-neck which improves orbit precision of LEO, so we can take combined orbit determination strategy of BPS and user satellites (LEO) to ameliorate precision. This paper integrates whole network adjustment algorithm into satellite precise orbit determination technology, and brings forward multi-LEO combined orbit determination

Deyong Zhao; Xiaogang Pan; Haiyin Zhou; Zhengming Wang

2005-01-01

170

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

171

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

172

Preliminary GPS orbit determination results for the Extreme Ultraviolet Explorer

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

173

A Keplerian approach to angles-only orbit determination

NASA Astrophysics Data System (ADS)

A method is derived from Kepler's laws of motion allowing the determination of slant range for orbiting targets given monocular angles-only measurements. The method is shown to work without knowledge of three parameters: universal gravitational constant, mass of the central body, and time scale. Monte Carlo trials with noisy data sets, however, show that the method is much more sensitive to measurement noise than competing methods that require knowledge of these parameters.

Vitarius, Patrick J.; Hahs, Daniel; Gregory, Don A.

2006-05-01

174

Improved DORIS accuracy for precise orbit determination and geodesy

NASA Technical Reports Server (NTRS)

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

Willis, Pascal; Jayles, Christian; Tavernier, Gilles

2004-01-01

175

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

176

NASA Astrophysics Data System (ADS)

The Lunar Reconnaissance Orbiter (LRO), launched June 18, 2009, carries the Lunar Reconnaissance Orbiter Camera (LROC) as one of seven remote sensing instruments on board. The camera system is equipped with a Wide Angle Camera (WAC) and two Narrow Angle Cameras (NAC) for systematic lunar surface mapping and detailed site characterization for potential landing site selection and resource identification. The LROC WAC is a pushframe camera with five 14-line by 704-sample framelets for visible light bands and two 16-line by 512-sample (summed 4x to 4 by 128) UV bands. The WAC can also acquire monochrome images with a 14-line by 1024-sample format. At the nominal 50-km orbit the visible bands ground scale is 75-m/pixel and the UV 383-m/pixel. Overlapping WAC images from adjacent orbits can be used to map topography at a scale of a few hundred meters. The two panchromatic NAC cameras are pushbroom imaging sensors each with a Cassegrain telescope of a 700-mm focal length. The two NAC cameras are aligned with a small overlap in the cross-track direction so that they cover a 5-km swath with a combined field-of-view (FOV) of 5.6°. At an altitude of 50-km, the NAC can provide panchromatic images from its 5,000-pixel linear CCD at a ground scale of 0.5-m/pixel. Calibration of the cameras was performed by using precision collimator measurements to determine the camera principal points and radial lens distortion. The orientation of the two NAC cameras is estimated by a boresight calibration using double and triple overlapping NAC images of the lunar surface. The resulting calibration results are incorporated into a photogrammetric bundle adjustment (BA), which models the LROC camera imaging geometry, in order to refine the exterior orientation (EO) parameters initially retrieved from the SPICE kernels. Consequently, the improved EO parameters can significantly enhance the quality of topographic products derived from LROC NAC imagery. In addition, an analysis of the spacecraft jitter effect is performed by measuring lunar surface features in the NAC CCD overlapping strip in the image space and object space. Topographic and cartographic data processing results and products derived from LROC NAC and WAC stereo imagery using different software systems from several participating institutions of the LROC team will be presented, including results of calibration, bundle adjustment, jitter analysis, DEM, orthophoto, and cartographic maps.

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

2009-12-01

177

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

178

Enhanced orbit determination filter sensitivity analysis: Error budget development

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

179

Astrometric positioning and orbit determination of geostationary satellites

NASA Astrophysics Data System (ADS)

In the project titled “Astrometric Positioning of Geostationary Satellite” (PASAGE), carried out by the Real Instituto y Observatorio de la Armada (ROA), optical observation techniques were developed to allow satellites to be located in the geostationary ring with angular accuracies of up to a few tenths of an arcsec. These techniques do not necessarily require the use of large telescopes or especially dark areas, and furthermore, because optical observation is a passive method, they could be directly applicable to the detection and monitoring of passive objects such as space debris in the geostationary ring.By using single-station angular observations, geostationary satellite orbits with positional uncertainties below 350 m (2 sigma) were reconstructed using the Orbit Determination Tool Kit software, by Analytical Graphics, Inc. This software is used in collaboration with the Spanish Instituto Nacional de Técnica Aeroespacial.Orbit determination can be improved by taking into consideration the data from other stations, such as angular observations alone or together with ranging measurements to the satellite. Tests were carried out combining angular observations with the ranging measurements obtained from the Two-Way Satellite Time and Frequency Transfer technique that is used by ROA’s Time Section to carry out time transfer with other laboratories. Results show a reduction of the 2 sigma uncertainty to less than 100 m.

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

2011-03-01

180

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

NASA Astrophysics Data System (ADS)

The precise orbit determination (POD) of low earth orbiter (LEO) has complied with its required positioning accuracy by the double-differencing of observations between International GNSS Service (IGS) and LEO to eliminate the common clock error of the global positioning system (GPS) satellites and receiver. Using this method, we also have achieved the 1 m positioning accuracy of Korea Multi-Purpose Satellite (KOMPSAT)-2. However double-differencing POD has huge load of processing the global network of lots of ground stations because LEO turns around the Earth with rapid velocity. And both the centimeter accuracy and the near real time (NRT) processing have been needed in the LEO POD applications--atmospheric sounding or urgent image processing--as well as the surveying. An alternative to differential GPS for high accuracy NRT POD is precise point positioning (PPP) to use measurements from one satellite receiver only, to replace the broadcast navigation message with precise post processed values from IGS, and to have phase measurements of dual frequency GPS receiver. PPP can obtain positioning accuracy comparable to that of differential positioning. KOMPSAT-5 has a precise dual frequency GPS flight receiver (integrated GPS and occultation receiver, IGOR) to satisfy the accuracy requirements of 20 cm positioning accuracy for highly precise synthetic aperture radar image processing and to collect GPS radio occultation measurements for atmospheric sounding. In this paper we obtained about 3-5 cm positioning accuracies using the real GPS data of the Gravity Recover and Climate Experiment (GRACE) satellites loaded the Blackjack receiver, a predecessor of IGOR. And it is important to reduce the latency of orbit determination processing in the NRT POD. This latency is determined as the volume of GPS measurements. Thus changing the sampling intervals, we show their latency to able to reduce without the precision degradation as the assessment of their precision.

Choi, Jong-Yeoun; Lee, Sang-Jeong

2011-03-01

181

Orbit determination support for Hiten's aerobraking in the Earth's atmosphere

NASA Technical Reports Server (NTRS)

Two passes of the ISAS (Japan's Institute of Space and Astronautical Science) Hiten spacecraft through the Earth's atmosphere, at perigee altitudes of 125 km and 120 km, during Mar. 1991 marked the first aerobraking technology demonstrations for an object in cis-lunar orbit traveling at near Earth escape velocity. Prediction and control of perigee altitude to better than 1 km was desired to assure spacecraft survival. Covariance analysis provided confidence that prediction accuracy better than 200 m for support of final trim maneuver design was achievable with NASA DSN (Deep Space Network) tracking support. ISAS used orbit determination results in their decisions to cancel final trim maneuvers. Post flight reconstructions, marking the first combined use of DSN and ISAS tracking data, yielded perigee altitude solutions which agree with the near real time mission operations support predictions to better than 50 m.

Efron, L.; Ellis, J.; Menon, P. R.; Tucker, B.

1991-01-01

182

TDRSS orbit determination using short baseline differenced carrier phase

NASA Technical Reports Server (NTRS)

This paper discusses a covariance study on the feasibility of using station-differenced carrier phase on short baselines to track the TDRSS satellites. Orbit accuracies for the TDRSS using station-differenced carrier phase data and range data collected from White Sands, NM are given for various configurations of ground stations and range data precision. A one-sigma-position position accuracy of 25 meters can be achieved using two orthogonal baselines of 100 km for the station-differenced phase data and range data with 1 m accuracy. Relevant configuration parameters for the tracking system and important sources of error are examined. The ability of these data to redetermine the position after a station keeping maneuver is addressed. The BRTS system, which is currently used for TDRSS orbit determination, is briefly described and its errors are given for comparison.

Nandi, S.; Edwards, C. D.; Wu, S. C.

1993-01-01

183

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

184

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

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

185

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

NASA Technical Reports Server (NTRS)

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

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

1998-01-01

186

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

2013-07-01

187

NASA Astrophysics Data System (ADS)

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

Jo, Jung Hyun

2002-09-01

188

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

NASA Astrophysics Data System (ADS)

The tremendous improvement of the gravity field models which we are achieving with the last Earth's satellite missions like, CHAMP, GRACE and GOCE devoted to its recovery could make feasibile the use of precise orbit determination (POD) of Earth satellites as a tool for sensing global changes of some key atmosphere parameters like refractivity and extinction. Such improvements indeed, coupled with the huge number of running Earth's satellites and combinations of their orbital parameters (namely the nodes) in a gravity field free fashion (hereafter GFF) can magnify the solar radiation pressure acting on medium earth orbit satellites :GPS, Etalon and, in near real future GALILEO and its smooth modulation through the Earth's atmosphere (penumbra). We would remind that The GFF technique is able to cancel out with "n" satellite orbital parameters the first n-1 even zonal harmonics of the gravity field. Previously it was demonstrated that the signal we want to detect could in principle emerge from the noise threshold but, more refined models of the atmosphere would be needed to perform a more subtle analysis. So we will re-compute the signal features of penumbra by applying more refined atmospheric models. The analysis will be performed by including in GFF Earth's satellites equipped with DORIS systems (Jason, Spot 2-3-4-5, ENVISAT etc.) other than those ranged with SLR and GPS. The introduction of DORIS tracked satellites indeed will allow to cancel higher and higher order of even zonal harmonics and will make still more favourable the signal to noise budget. The analysis will be performed over a time span of at least few tens of years just to enhance probable climate signatures.

Vespe, Francesco

189

Radiation force modeling for ICESat precision orbit determination

NASA Astrophysics Data System (ADS)

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

Webb, Charles Edward

190

Galileo orbit determination for the Venus and Earth-1 flybys

NASA Astrophysics Data System (ADS)

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

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

1992-08-01

191

Reduced-dynamic orbit determination and the use of accelerometer data

Reduced-dynamic orbit determination for low Earth orbiting satellites is usually performed to obtain trajectories of highest accuracy without making use of additional accelerometer data. We use efficient stochastic orbit modeling techniques based on least squares estimation to compare estimated piecewise constant accelerations of the CHAMP satellite with measurements from the STAR accelerometer to have an alternative orbit quality assessment. Stimulated

Adrian Jäggi; G. Beutler; U. Hugentobler

2005-01-01

192

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

193

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

194

Determination of the inflight OTF of orbital earth resources sensors

NASA Technical Reports Server (NTRS)

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

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

1972-01-01

195

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

NASA Technical Reports Server (NTRS)

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

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

1986-01-01

196

Relative performance of algorithms for autonomous satellite orbit determination

NASA Astrophysics Data System (ADS)

Limited word size in contemporary microprocessors causes numerical problems in autonomous satellite navigation applications. Numerical error introduced in navigation computations performed on small wordlength machines can cause divergence of sequential estimation algorithms. To insure filter reliability, square root algorithms have been adopted in many applications. The optimal navigation algorithm requires a careful match of the estimation algorithm, dynamic model, and numerical integrator. In this investigation, the relationship of several square root filters and numerical integration methods is evaluated to determine their relative performance for satellite navigation applications. The numerical simulations are conducted using the Phase I GPS constellation to determine the orbit of a LANDSAT-D type satellite. The primary comparison is based on computation time and relative estimation accuracy.

Tapley, B. D.; Peters, J. G.; Schutz, B. E.

1981-03-01

197

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

198

Determination of Orbitals for Use in Configuration Interaction Calculations.

National Technical Information Service (NTIS)

For a full configuration interaction (CI) calculation the choice of orbitals is completely irrelevant, i.e., the calculated wavefunction is unaffected by an arbitrary unitary transformation of the orbitals; it depends only on the space spanned by the orig...

T. H. Dunning E. R. Davidson K. Ruedenberg J. Hinze

1978-01-01

199

Advances in precision orbit determination of GRACE satellites

NASA Astrophysics Data System (ADS)

The twin Gravity Recovery And Climate Experiment (GRACE) satellites carry a complete suite of instrumentation essential for precision orbit determination (POD). Dense, continuous and global tracking is provided by the Global Positioning System receivers. The satellite orientation is measured using two star cameras. High precision measurements of non-gravitational accel-erations are provided by accelerometers. Satellite laser ranging (SLR) retroreflectors are used for collecting data for POD validation. Additional validation is provided by the highly precise K-Band ranging system measuring distance changes between the twin GRACE satellites. This paper presents the status of POD for GRACE satellites. The POD quality will be vali-dated using the SLR and K-Band ranging data. The POD quality improvement from upgraded modeling of the GPS observations, including the transition to the new IGS05 standards, will be discussed. In addition, the contributions from improvements in the gravity field modeling -partly arising out of GRACE science results -will be discussed. The aspects of these improve-ments that are applicable for the POD of other low-Earth orbiting satellites will be discussed as well.

Bettadpur, Srinivas; Save, Himanshu; Kang, Zhigui

200

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

201

GPS-based Orbit Determination for LEO Using AKF Bidirectional Filter

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

Xian-Ping Qin; Yuan-Xi Yang

2010-01-01

202

Study of Geopotential Error Models Used in Orbit Determination Error Analysis.

National Technical Information Service (NTIS)

The uncertainty in the geopotential model is currently one of the major error sources in the orbit determination of low-altitude Earth-orbiting spacecraft. The results of an investigation of different geopotential error models and modeling approaches curr...

C. Yee D. Kelbel T. Lee M. V. Samii G. D. Mistretta

1991-01-01

203

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

204

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

205

NASA Technical Reports Server (NTRS)

The possibility of initiating the growth of ice sheets by solar insolation variations is examined. The study is conducted using a climate model with three different orbital configurations corresponding to 116,000 and 106,000 yr before the present and a modified insolation field with greater reductions in summer insolation at high northern latitudes. Despite the reduced summer and fall insolation, the model fails to maintain snow cover through the summer at locations of suspected ice sheet initiation. The results suggest that there is a discrepancy between the model's response to Milankovitch perturbations and the geophysical evidence of ice sheet initiation. If the model results are correct, the growth of ice shown by geophysical evidence would have occurred in an extremely ablative environment, demanding a complicated strategy.

Rind, D.; Peteet, D.; Kukla, G.

1989-01-01

206

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

To define an appropriate orbit support procedure for the DSPSE mission, detailed permission orbit determination covariance analyses have been performed for the translunar and trans-Geographos mission phases. Preliminary analyses were also performed for the lunar mapping mission phase. These analyses are designed to assess the tracking patterns and the amount of tracking data needed to obtain orbit solutions of required

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

1993-01-01

207

ERS-1 and ERS-2 tandem mission: Orbit determination, prediction and maintenance

After a short summary of the successful orbit operations during the ERS-2 Launch and Early Orbit Phase, the transition to and implementation of the tandem mission for the two satellites is described, including a comparison of the required and achieved ground track spacing. The new implementation of the routine operational and precise orbit determination and prediction systems is presented briefly,

R Zandbergen; J. M Dow; M Romay Merino; R Píriz; F Martínez Fadrique

1997-01-01

208

ERS-1 and ERS-2 tandem mission: orbit determination, prediction and maintenance

After a short summary of the successful orbit operations during the ERS-2 Launch and Early Orbit Phase, the transition to and implementation of the tandem mission for the two satellites is described, including a comparison of the required and achieved ground track spacing. The new implementation of the routine operational and precise orbit determination and prediction systems is presented briefly,

R. Zandbergen; J. M. Dow; M. Romay Merino; R. Píriz; F. Martínez Fadrique

1997-01-01

209

Contribution of SLR tracking data to GNSS orbit determination

GNSS orbits derived from microwave tracking data may be validated using SLR range measurements. Recent validation results show mean range residuals of several centimeters, as well as significant seasonal variations for the two GPS satellites that are equipped with retroreflector arrays. These differences may be assigned to orbit or observation modeling problems, or both. In order to study this issue,

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

2007-01-01

210

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

211

The impact of accelerometry on CHAMP orbit determination

NASA Astrophysics Data System (ADS)

The contribution of the STAR accelerometer to the CHAMP orbit precision is evaluated and quantified by means of the following results: orbital fit to the satellite laser ranging (SLR) observations, GPS reduced-dynamic vs SLR dynamic orbit comparisons, and comparison of the measured to the modeled non-gravitational accelerations (atmospheric drag in particular). In each of the four test periods in 2001, five CHAMP arcs of 2 days' length were analyzed. The mean RMS-of-fit of the SLR observations of the orbits computed with STAR data or the non-gravitational force model were 11 and 24 cm, respectively. If the accelerometer calibration parameters are not known at least at the few percent level, the SLR orbit fit deteriorates. This was tested by applying a 10% error to the along-track scale factor of the accelerometer, which increased the SLR RMS-of-fit on average to 17 cm. Reference orbits were computed employing the reduced-dynamic technique with GPS tracking data. This technique yields the most accurate orbit positions thanks to the estimation of a large number of empirical accelerations, which compensate for dynamic modeling errors. Comparison of the SLR orbits, computed with STAR data or the non-gravitational force model, to the GPS-based orbits showed that the SLR orbits employing accelerometer observations are twice as accurate. Finally, comparison of measured to modeled accelerations showed that the level of geomagnetic activity is highly correlated with the atmospheric drag model error, and that the largest errors occur around the geomagnetic poles.

Bruinsma, S.; Loyer, S.; Lemoine, J. M.; Perosanz, F.; Tamagnan, D.

2003-05-01

212

TLE-Aided Orbit Determination Using Single-Station SLR Data

NASA Astrophysics Data System (ADS)

It is difficult to use the single-station satellite laser ranging (SLR) data for orbit determination, due to the singular geometrical distribution of the observations. The single-station data produced by performing the diffuse- reflection SLR on the earth-orbiting space debris are therefore ineffective for orbit improvement. To solve this problem, we propose an orbit determination method by using single-station SLR data in aid of the two-line element set (TLE). For verifying its feasibility, this method is implemented and applied to the orbit determination of the satellite Ajisai, using the single-station SLR data of five passes in one day and the corresponding TLE. And on this basis, the five-day orbit prediction is generated, the result indicates that the errors of predicted positions are less than 40 m. In addition, the potential application of this method in the orbit improvement of space debris is discussed.

Liang, Zhi-peng; Liu, Cheng-zhi; Fan, Cun-bo; Sun, Ming-guo

2012-10-01

213

NASA Technical Reports Server (NTRS)

Differencing multiple, simultaneous Tracking and Data Relay Satellite System (TDRSS) one-way Doppler passes can yield metric tracking data usable for orbit determination for (low-cost) spacecraft which do not have TDRSS transponders or local oscillators stable enough to allow the one-way TDRSS Doppler tracking data to be used for early mission orbit determination. Orbit determination error analysis results are provided for low Earth orbiting spacecraft for various early mission tracking scenarios.

Marr, Greg C.

2003-01-01

214

[Craniopantograph--an instrument for determination of orbit shape].

The authors describe the structure of principles of function of a measuring-recording instruments, so called craniopantograph. The instrument of own design serves for examination of the spatial variability of the orbit. The obtained measurements of the internal shape of the orbit can be processed later by microcomputer technique. For construction of craniopantograph the principles of function of two typical instruments--craniometer and pantograph were used. PMID:2104332

Reymond, J; Piasecki, K; Wanyura, H

1990-02-01

215

Continuing work initiated in an earlier publication [Y. Torigoe, K. Hattori, and H. Asada, Phys. Rev. Lett. 102, 251101 (2009)], gravitational wave forms for a three-body system in Lagrange's orbit are considered especially in an analytic method. First, we derive an expression of the three-body wave forms at the mass quadrupole, octupole, and current quadrupole orders. By using the expressions, we solve a gravitational-wave inverse problem of determining the source parameters to this particular configuration (three masses, a distance of the source to an observer, and the orbital inclination angle to the line of sight) through observations of the gravitational wave forms alone. For this purpose, the chirp mass to a three-body system in the particular configuration is expressed in terms of only the mass ratios by deleting initial angle positions. We discuss also whether and how a binary source can be distinguished from a three-body system in Lagrange's orbit or others.

Asada, Hideki [Faculty of Science and Technology, Hirosaki University, Hirosaki 036-8561 (Japan)

2009-09-15

216

Orbits of four visual binaries determined from observations along short arcs

NASA Astrophysics Data System (ADS)

The orbits of the four visual binaries ADS 246 (GL 15), ADS 7724 ( ? Leo), ADS 10386 (GJ 659), and ADS 14909 (1 Peg) have been determined using the apparent motion parameters (AMP) method. The orbital periods of these stars are 1200, 550, 7500, and 18 000 yr, respectively. The orbits were calculated based on observations along short arcs obtained with the 26-inch refractor of the Pulkovo Observatory and Hipparcos parallaxes, supplemented with radial-velocity measurements for the components of these pairs taken from the literature. All visual and photographic observations of these stars after 1830 from the WDS catalog have been taken into consideration. The new orbits of ADS 246 and ADS 7724 are compared with the orbits computed in other studies. The orbits of ADS 10386 and ADS 14909 have been determined for the first time. The orientation of the planes of the computed orbits in Galactic coordinates have also been calculated.

Romanenko, L. G.; Kiselev, A. A.

2014-01-01

217

NASA Astrophysics Data System (ADS)

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

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

2014-07-01

218

New Technique for Determining the Shock Initiation Sensitivity of Explosives.

National Technical Information Service (NTIS)

A new technique for determining the shock initiation sensitivity of explosives is described. It involves a flyer plate impinging upon the test explosive to induce initiation of detonation. An electrically exploded foil propels the flyer plate, which is a ...

A. C. Schwarz

1977-01-01

219

The a posteriori estimation of stochastic model in statistical orbit determination

The determination of the precise orbits of artificial satellites by taking advantage of several types of satellite tracking techniques has become a tendency today. Especially for multidisciplinary satellites, in order to guarantee their success, several tracking equipments are usually collocated. In the precision orbit determinations (POD) by using either single or multiple kinds of tracking techniques, there always exists a

Feipeng Zhang; Cheng Huang; Yaqin Li; Chugang Feng; Yuanlan Zhu

2000-01-01

220

This paper deals with an advanced Kalman filter application to orbit determination from satellite tracking data. Modern control theory is used to set up an optimal Kalman gain for the estimation problem and to estimate its errors out of the system outputs. The classical orbit determination techniques have been used over the years for the evaluation of data analysis. A

Robert D. Culp; Don Mackison; Ho-Ling Fu

1991-01-01

221

Comparison of ERBS Orbit Determination Accuracy Using Batch Least-Squares and Sequential Methods.

National Technical Information Service (NTIS)

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 over...

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

1991-01-01

222

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

223

First Orbit and Mass Determinations for Nine Visual Binaries

NASA Astrophysics Data System (ADS)

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.

2012-01-01

224

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

225

Orbit Determination with the two-body Integrals

We investigate a method to compute a finite set of preliminary orbits for solar system bodies using the first integrals of the Kepler problem. This method is thought for the applications to the modern sets of astrometric observations, where often the information contained in the observations allows only to compute, by interpolation, two angular positions of the observed body and

Giovanni Federico Gronchi; Linda Dimare; Andrea Milani

2009-01-01

226

Prospects for an orbital determination and capture cell experiment

A dust experiment which combines measurements of the elemental and isotopic composition of individual particles with orbital information would contribute fundamental, new scientific information on the sources contributing to the micrometeoroid population. The general boundary conditions for such a system are: (1) it must be capable of measuring velocities in the range of 10 km\\/sec to 100 km\\/sec with several

W. C. Carey; R. M. Walker

1986-01-01

227

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

228

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

229

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

230

Determination of Orbiter and Carrier Aerodynamic Coefficients from Load Cell Measurements

NASA Technical Reports Server (NTRS)

A method of determining orbiter and carrier total aerodynamic coefficients from load cell measurements is required to support the inert and the captive active flights of the ALT program. A set of equations expressing the orbiter and carrier total aerodynamic coefficients in terms of the load cell measurements, the sensed dynamics of the Boeing 747 (carrier) aircraft, and the relative geometry of the orbiter/carrier is derived.

Glenn, G. M.

1976-01-01

231

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

D. M. Lucchesi

2007-01-01

232

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

D. M. Lucchesi

2007-01-01

233

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

D. M. Lucchesi

2006-01-01

234

This study applies the work of John E. Draim in looking at an unique high altitude satellite constellation of elliptical orbits, which provides continuous global coverage, and considers the mission application of satellite to satellite tracking for this four satellite constellation. Such an application could provide precise, timely and affordable orbit determination services to a variety of low Earth orbit

Douglas Roger Tighe

1986-01-01

235

Hybrid precision orbit determination for low altitude satellites by GPS tracking

NASA Astrophysics Data System (ADS)

A numerical simulation study was performed in order to investigate the effects of process noise modeling on state estimates of a Low Earth Orbiting (LEO) satellite in the GPS-based hybrid Precise Orbit Determination (POD) strategy. The use of simulated data enabled the creation of the simulated data with three different correlation types of the unknown forces, which were constant in magnitude, exponentially decreasing and periodical with exponential decrement. The hybrid POD results obtained with first order Gauss-Markov random process and periodic random process were mutually compared to assess their relative performance under the same condition. The simulation results indicate that the hybrid POD strategy with a periodic random process provides an improvement over that with a first order Gauss-Markov random process for the three cases studied, particularly for the unknown force with periodical behavior. Application of the hybrid POD strategy to the CHAMP satellite was conducted. The CHAMP GPS tracking and a ground station network of thirty-five GPS tracking stations were processed to yield a five day CHAMP ephemeris. The hybrid POD results obtained from processing the real CHAMP tracking data showed the improved performance of periodic random process over first order Gauss-Markov random process. Measures such as orbit comparison with other high accuracy orbit solutions and SLR residual analysis were taken to assess the radial orbit accuracy of the hybrid orbit solution. As a relative measure of orbit accuracy, the orbit comparison of the hybrid orbit solution to the MSODP reference orbit solution was made and the results indicate that the radial orbit accuracy of the hybrid solution is within 6 cm in an RMS sense. As an absolute measure of orbit accuracy, the SLR residual analysis was performed and the results indicate that the radial orbit accuracy of the hybrid solution is at the level of 3--4 cm RMS, for the CHAMP orbit with 460 km altitude.

Lee, Seung-Woo

236

Orbit determination with the two-body integrals

We investigate a method to compute a finite set of preliminary orbits for solar system bodies using the first integrals of\\u000a the Kepler problem. This method is thought for the applications to the modern sets of astrometric observations, where often\\u000a the information contained in the observations allows only to compute, by interpolation, two angular positions of the observed\\u000a body and

Giovanni Federico Gronchi; L. Dimare; A. Milani

2010-01-01

237

Combined determination of orbit and accelerometer calibration parameters for CHAMP

Highest quality reduced-dynamic orbits for CHAMP may be obtained without any use of additional accelerometer data. In this case a considerably large number of so-called pseudo-stochastic parameters (e.g., piecewise constant or piecewise linear accelerations) compensate for deficiencies in the dynamic model. The excellent agreement between such estimated accelerations and measured accelerations from the STAR accelerometer rises the question how a

A. Jaeggi; U. Hugentobler; G. Beutler

2004-01-01

238

Calibration of GOCE Accelerometers by Precise Orbit Determination

NASA Astrophysics Data System (ADS)

The European Space Agency (ESA) Gravity field and steady-state Ocean Circular Explorer (GOCE) carries a gradiometer consisting of three pairs of accelerometers in an orthogonal triad. Precise GOCE science orbit solutions (PSO), which are based on Satellite-to-Satellite Tracking (SST) observations by the Global Positioning System (GPS) and which are claimed to be at the few cm precision level, have been used to calibrate the observations taken by the accelerometers. This has been done for each individual accelerometer by a dynamic orbit fit of the time series of position coordinates from the PSOs, where the accelerometer observations represent the non-gravitational accelerations. Since the individual accelerometers do not coincide with the center of mass of the GOCE satellite, the observations have to be corrected for rotational and gravity gradient terms. This is opposed to using the so-called common-mode accelerations, provided the center of the gradiometer coincides with the center of mass. Dynamic orbit fits based on these common-mode accelerations therefore served as reference. It will be shown that for all individual accelerometers similar dynamic orbit fits can be obtained comparable to the fits achieved using the common-mode accelerations, provided the above mentioned corrections are made. In addition, attention will be paid to the possibility of estimating accelerometer calibration parameters, such as biases and scale factors. Furthermore, an assessment was made of remaining gravity field modeling errors on the estimates of the calibration parameters. Acknowledgment. The European Space Agency is acknowledged for supporting this study and providing the GOCE observations.

Visser, P. N.

2012-12-01

239

GPS orbit determination at the National Geodetic Survey

NASA Technical Reports Server (NTRS)

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

Schenewerk, Mark S.

1992-01-01

240

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

241

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

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

2006-01-01

242

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

NASA Astrophysics Data System (ADS)

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.

1991-10-01

243

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

244

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

245

A Seasat data arc is analyzed in order to: gain experience in computing accurate orbits from laser ranging data; assess gravity and surface force model accuracy; determine the positions of five European Doppler stations relative to a global NASA ground station coordinate solution; and study the effects of European Doppler range-rate data on the orbital solution. The PGS S3 and

K. F. Wakker; B. A. C. Ambrosius; T. Vanderploeg

1981-01-01

246

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

247

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

Sander Goossens; Koji Matsumoto

2007-01-01

248

NASA Technical Reports Server (NTRS)

This paper provides an overview of the launch and early orbit activities performed by the NASA Goddard Space Flight Center's (GSFC) Flight Dynamics Facility (FDF) in support of five probes comprising the Time History of Events and Macroscale Interactions during Substorms (THEMIS) spacecraft. The FDF was tasked to support THEMIS in a limited capacity providing backup orbit determination support for validation purposes for all five THEMIS probes during launch plus 30 days in coordination with University of California Berkeley Flight Dynamics Center (UCB/FDC). The FDF's orbit determination responsibilities were originally planned to be as a backup to the UCB/FDC for validation purposes only. However, various challenges early on in the mission and a Spacecraft Emergency declared thirty hours after launch placed the FDF team in the role of providing the orbit solutions that enabled contact with each of the probes and the eventual termination of the Spacecraft Emergency. This paper details the challenges and various techniques used by the GSFC FDF team to successfully perform orbit determination for all five THEMIS probes during the early mission. In addition, actual THEMIS orbit determination results are presented spanning the launch and early orbit mission phase. Lastly, this paper enumerates lessons learned from the THEMIS mission, as well as demonstrates the broad range of resources and capabilities within the FDF for supporting critical launch and early orbit navigation activities, especially challenging for constellation missions.

Morinelli, Patrick; Cosgrove, jennifer; Blizzard, Mike; Nicholson, Ann; Robertson, Mika

2007-01-01

249

NASA Technical Reports Server (NTRS)

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

Wu, Jiun-Tsong; Yunck, Thomas P.

1992-01-01

250

Satellite Orbit Determination Using GPS Carrier Phase in Pure Kinematic Mode

NASA Astrophysics Data System (ADS)

The mainstream approach to satellite orbit determination has been a dynamic one. This approach is fine as long as the satellite dynamic model is accurate. When the dynamics model is not accurate, the reduced dynamic approach is better suited for orbit determination. Even a purely kinematic solution can be obtained by using the reduced dynamic approach. However, this method is computationally very extensive and still requires a reasonably good satellite dynamics model to compute its reference orbit. A new algorithm and computer program, KODAC (Kinematic Orbit Determination And Comparison), was developed for satellite orbit determination using a kinematic approach with the GPS carrier phase as observable. Since the GPS signal has enough spatial geometric information, it is possible to determine the satellite orbit using a purely kinematic approach. In this method both double and triple differenced GPS carrier phases are used as observables, and epoch by epoch satellite positions and DD ambiguities are estimated by assuming GPS ephemerides and ground station positions are known. TOPEX GPS data is used for this study, and the final radial rms orbit accuracy of 5 cm with respect to the MSODP (Multi Satellite Orbit Determination Program) dynamic solution is achieved. This new kinematic approach has the advantage of having consistent orbit accuracy regardless of satellite altitude. The same algorithm can be applied to any satellite with a GPS receiver due to the algorithm's non-dynamic approach. The TOPEX on-board receiver has only six channels, and its signal view angle is limited. With an improved on-board receiver equipped with more channels and a wider GPS view angle, an improvement in orbit accuracy can be expected for future satellite missions.

Byun, Sung Hun

251

Influence of the residual accuracy measure on determination of EAS orbits.

NASA Astrophysics Data System (ADS)

Currently, probabilistic and guaranteeing approaches are used to devise methods for determining orbits and choosing error distribution laws. The leading role is given to probability theory methods rather than to qualitative celestial mechanics methods. As a result, solutions that almost always differ from the true solutions are obtained, and secular error components inevitably arise in the precalculated satellite ephemerides. Moreover, secular components also arise due to theoretical methodical errors associated with the development of a mathematical formalism for the precise determination of orbits. In this paper, some aspects of determining the "bestfit" satellite orbits, free of secular error components in the precalculated satellite ephemerides, are considered.

Makarenko, F. A.

1997-12-01

252

Present status and future trends in near-Earth satellite orbit determination

NASA Astrophysics Data System (ADS)

The major components of an orbit determination system and the evolution of the elements making up each component are reviewed. Typical accuracies presently achievable in the orbit determination process, the factors limiting the accuracies, and improvements in the dynamic models used in the process are summarized. Models are developed for orbit determination programs which include: (1) time varying area for solar radiation pressure; (2) a time varying model for albedo radiation pressure; (3) Earth tides which account for the distortions in the Earth's body due to Sun and Moon attraction; and (4) ocean tides which affect satellite altimeter data.

Fuchs, A. J.

1981-08-01

253

Present status and future trends in near-Earth satellite orbit determination

NASA Technical Reports Server (NTRS)

The major components of an orbit determination system and the evolution of the elements making up each component are reviewed. Typical accuracies presently achievable in the orbit determination process, the factors limiting the accuracies, and improvements in the dynamic models used in the process are summarized. Models are developed for orbit determination programs which include: (1) time varying area for solar radiation pressure; (2) a time varying model for albedo radiation pressure; (3) Earth tides which account for the distortions in the Earth's body due to Sun and Moon attraction; and (4) ocean tides which affect satellite altimeter data.

Fuchs, A. J.

1981-01-01

254

Periodic-orbit determination of dynamical correlations in stochastic processes.

It is shown that the large-deviation statistical quantities of the discrete-time, finite-state Markov process P_{n+1};{(j)}= summation _{k=1};{N}H_{jk}P_{n};{(k)} , where P_{n};{(j)} is the probability for the j state at the time step n and H_{jk} is the transition probability, completely coincide with those from the Kalman map corresponding to the above Markov process. Furthermore, it is demonstrated that, by using simple examples, time correlation functions in finite-state Markov processes can be well described in terms of unstable periodic orbits embedded in the equivalent Kalman maps. PMID:17995080

Kobayashi, Miki U; Fujisaka, Hirokazu; Miyazaki, Syuji

2007-10-01

255

Correlation and orbit determination of space objects based on sparse optical data

NASA Astrophysics Data System (ADS)

While building up a catalogue of Earth-orbiting objects, the available optical observations are typically sparse. In this case, 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). The algorithms allow the accurate orbit determination by full least-squares solutions with all six orbital elements. The presence of a significant subpopulation of high area-to-mass ratio objects in the GEO region, strongly affected by non-gravitational perturbations, required to solve also for dynamical parameters describing these effects, that is to fit between six and eight free parameters for each orbit. The validation was based upon a set of real data, acquired from the European Space Agency (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. This would allow a survey strategy covering the region of interest in the sky just once per night. As a result, it would be possible to significantly reduce the requirements for a future telescope network, with respect to what would have been required with the previously known algorithms for correlation and orbit determination.

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

2011-11-01

256

Precise orbit determination of Smart-1 and Chang'E-1

NASA Astrophysics Data System (ADS)

The Smart-1 was tracked by Chinese VLBI network and USB stations from 28 May, 2006 to 2 June, 2006 as a test for Chinese deep space network tracking ability, precise orbit determination was processed combining VLBI delay, delay rate and Doppler data. The reaction wheel unloadings were considered in long arc orbit determination, it showed good consistency with reconstructed orbit provided by ESA, the strategy used in smart-1 was used in Chang'E-1 precise orbit determination. Chang'E-1 was launched at 24 Oct, 2007, one of the main scientific objections is to map the lunar surface and get 3-D lunar topography model by satellite laser altimetry. The precise orbit determination of Chang'E-1 was realized by combining VLBI and USB data using GEODYNII/SOVLE software of GSFC/NASA/USA (Rowland,1997; Ullman,1994),, the frequently reaction wheel unloadings are considered in order to get high accuracy and continuous orbit, which can attribute to the laser altimetry data process and possible lunar gravity field recovery. Keywords: smart-1, Chang'E-1, precise orbit determination, reaction wheel unloading

Jianguo, Yan; Ping, Jing-Song; Li, Fei

257

Orbit determination for Magellan and Pioneer 12 using same-beam interferometry

NASA Technical Reports Server (NTRS)

Simultaneous tracking of two spacecraft in orbit about a distant planet, by two widely-separated earth-based radio antennas, provides more accurate positioning information than can be obtained by tracking each spacecraft separately. A demonstration of this tracking technique, referred to as Same-Beam Interferometry (SBI), is in progress using the Magellan and Pioneer 12 orbiters at Venus. Signals from both spacecraft fall within the same beamwidth of the earth-based tracking antennas. The plane-of-sky position difference between spacecraft is precisely determined by double-differenced phase measurements. This data type complements line-of-sight Doppler. Data were collected from Magellan and Pioneer 12 on Aug. 11-12, 1990, shortly after Magellan was inserted into Venus orbit. Orbits for both spacecraft were fit with one day data arc using Doppler and SBI data and compared to orbits fit to only Doppler data. The Doppler plus SBI orbits show improved orbit-to-orbit consistency over the Doppler-only orbits.

Folkner, W. M.; Engelhardt, D. B.; Border, J. S.; Mottinger, N. A.

1992-01-01

258

Orbit determination for Magellan and Pioneer 12 using same-beam interferometry

NASA Astrophysics Data System (ADS)

Simultaneous tracking of two spacecraft in orbit about a distant planet, by two widely-separated earth-based radio antennas, provides more accurate positioning information than can be obtained by tracking each spacecraft separately. A demonstration of this tracking technique, referred to as Same-Beam Interferometry (SBI), is in progress using the Magellan and Pioneer 12 orbiters at Venus. Signals from both spacecraft fall within the same beamwidth of the earth-based tracking antennas. The plane-of-sky position difference between spacecraft is precisely determined by double-differenced phase measurements. This data type complements line-of-sight Doppler. Data were collected from Magellan and Pioneer 12 on Aug. 11-12, 1990, shortly after Magellan was inserted into Venus orbit. Orbits for both spacecraft were fit with one day data arc using Doppler and SBI data and compared to orbits fit to only Doppler data. The Doppler plus SBI orbits show improved orbit-to-orbit consistency over the Doppler-only orbits.

Folkner, W. M.; Engelhardt, D. B.; Border, J. S.; Mottinger, N. A.

1992-08-01

259

Real Time, Autonomous, Precise Orbit Determination Using the Global Positioning System.

National Technical Information Service (NTIS)

In an effort to estimate precise satellite ephemeris in real-time on board a satellite, the Goddard Space Flight Center (GSFC) created the GPS enhanced Orbit Determination Experiment (GEODE) flight navigation software. This dissertation offers alternative...

D. B. Goldstein

2000-01-01

260

GPS-based Orbit Determination for LEO Using AKF Bidirectional Filter

NASA Astrophysics Data System (ADS)

In the paper, the principle of GPS-based orbit determination for low earth orbiter (LEO) using adaptive Kalman filtering (AKF) is introduced. The difference of AKF with reduced dynamic technique (RDT) in LEO precise orbit determination (POD) is analyzed. The arithmetic of using bidirectional filter to improve AKF and RDT POD is put forward. Adopting AKF bidirectional filter and RDT bidirectional filter?two GRACE satellites orbits are determined by using the on-board GPS data observed from March 31 to April 4, 2004. When the orbits of two GRACE satellites are computed, the IERS Convention 2000 is closely followed. The EIGEN2 gravity model is employed. JPL planetary ephemeris DE403/LE403 is adopted. DTM94 is used as the empirical atmospheric density model. A simple ball model is used to compute solar radiation pressure. The zero-differenced ionosphere free carrier phase observations (taken at the 30 second processing interval) is processed when using AKF/RDT bidirectional filter to compute GRACE satellites orbits. When using RDT bidirectional filter POD, the total size of the filter state is always equal to 12+n, which including 6-dimensional spacecraft state, 3 empirical accelerations, 1 atmospheric drag coefficient, 1 solar radiation pressure coefficient, 1 receiver clock offset and n ionosphere free carrier phase biases. While the total size of the filter state is always equal to 7+n, which including 6-dimensional spacecraft state, 1 receiver clock offset and n ionosphere free carrier phase biases, when satellite orbit determination using AKF bidirectional filter. The results are compared with the orbits provided by JPL and independently validated with satellite laser range (SLR) data. By comparison and analysis, we find that when satellite orbit determination using AKF bidirectional filter, the orbit precision of GRACE-A and GRACE-B is better than 10 cm in 3-Dimension position, and is about 5 cm in radial(R), transverse(T) and normal(N) direction respectively. We also find that the influence of the measurement outliers on AKF bidirectional filter POD is less than that on RDT bidirectional filter POD. The results of AKF bidirectional filter POD are more smoothed than the results of RDT bidirectional filter POD. The precision of the orbit from the EKF bidirectional filter is better than that from the RDT bidirectional filter. Keywords: Global Positioning System, low earth orbiter, satellite orbit determination, adaptive filtering

Qin, Xian-Ping; Yang, Yuan-Xi

2010-05-01

261

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

262

A determination of the orbit of GX 301-2. [binary X-ray pulsars

NASA Technical Reports Server (NTRS)

The pulse phase of GX 301-2(4U 1223-62) was tracked for 30 days with the SAS 3 satellite during 1979 January and February. It is suggested that most of the observed changes in pulse period are the result of Doppler shifts in a binary orbit, as opposed to changes in the intrinsic pulse period alone. The SAS 3 data allow orbital periods P(orb) equal to or greater than 23 days when a constant rate of change in the intrinsic pulse period is allowed as a free parameter in the orbital fits. For each trial orbital period the other orbital elements of the binary system are well determined. The SAS 3 data is combined with the Ariel 5 pulse arrival-time data to further restrict the allowed orbits. In both data sets a sharp minimum is observed in the Doppler delays of the pulse arrival times. Evidence is presented that the correct orbit is most likely the one with P(orb) = 35.0d, a projected semimajor axis for the neutron star of 304 light-seconds, and an eccentricity of 0.44. The relation of this system to the six X-ray binaries whose orbits have been determined previously is also discussed.

Kelley, R.; Rappaport, S.; Petre, R.

1980-01-01

263

Optimal weighting of a priori statistics in quick-look orbit determination

Methods are developed which provide for the 'optimal' weighting of the a priori covariance used in quick-look orbit determination problems. The methods are demonstrated by an application to a quick-look orbit determination simulation, and the results are compared to those obtained by conventional minimum-variance solution techniques. The results demonstrate the potential improvement in the estimated accuracy that can be achieved

David A. Cicci

1993-01-01

264

This paper describes an investigation and comparison of the approach-phase orbit determination performance of delta-Very Long Baseline Interferometry (delta VLBI) and Connected Element Interferometry (CEI) data types when used in conjunction with conventional two-way Doppler data. Simulated data sets containing Doppler plus delta VLBI data and Doppler plus CEI data are used to calculate approximate orbit determination accuracy statistics for

Sam W. Thurman; Catherine B. Sybert

1992-01-01

265

Study of geopotential error models used in orbit determination error analysis

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

266

New technique for determining the shock initiation sensitivity of explosives

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

1977-01-01

267

NASA Astrophysics Data System (ADS)

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

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

1994-04-01

268

Precise orbit determination of Compass-M1: a primary result

NASA Astrophysics Data System (ADS)

On April 13, 2007, the first experiment satellite, Compass-M1, of China's the second generation Compass Navigation system was successfully launched. Unlike previous Compass satellites, Compass-M1 is the first satellite in medium earth orbit (MEO), and broadcast navigation signals in multi-frequencies in L-band. If signals were received from more than four satellites, users can determine their locations in a passive manner like using GPS. A primary result of precise orbit determination of Compass-M1 is presented in this paper. Five tracking stations, all located in China, are used. Double-frequency code and carrier phase observations are processed in zero-difference mode. Receiver and satellite clocks are modeled by linear or quadratic polynomial. The radiation pressure model is the so-called extended CODE orbit model, and an a priori model is introduced according to the size and physical attribute of Compass-M1. The solution is based on 3-day arc dynamical precise orbit determination. Estimated parameters include six keplerian orbit elements, two radiation pressure model parameters and clock polynomial coefficients. Orbit overlap difference and validating with SLR indicate that the accuracy of the precise orbit is quite exciting and exceeds our expectation.

Sun, Baoqi

269

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

270

NASA Astrophysics Data System (ADS)

As a special approach to orbit determination for satellites with spaceborne GPS receivers, the kinematic Precise Orbit Determination (POD) is independent of any mechanical model (e.g., the Earth gravity ?eld, atmospheric drag, solar radiation pressure, etc.), and thus especially suitable for the orbit determination of Low Earth Orbiting (LEO)satellites perturbed strongly bythe atmosphere. In this paper, based on the space-borne dual-frequency GPS data, we study the kinematic POD, discuss the pre-processing of the data, and construct an algorithm of zero-difference kinematic POD. Using the observational data from GRACE (Gravity Recovery And Climate Experiment) satellites covering the whole month of February 2008, we verify the effectiveness and reliability of this algorithm. The results show that the kinematic POD may attain an accuracy of about 5 cm (with respect to satellite laser ranging data), which is at the same level as the dynamic and reduced-dynamic PODs

Peng, Dong-ju; Wu, Bin

2012-07-01

271

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

National Technical Information Service (NTIS)

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 ca...

J. Fulbright J. McIntire J. Xiong N. Lei S. Lee V. Chiang Z. Wang

2012-01-01

272

NASA Astrophysics Data System (ADS)

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

Ren, Shulin; Fu, Yanning

2010-05-01

273

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

Deyong Zhao; Hongmei Yu

2010-01-01

274

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

275

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

NASA Astrophysics Data System (ADS)

Today more and more Low Earth orbiting satellites (LEOs) of new scientific missions are equipped with a GPS receiver for precise orbit determination (POD), on-board GPS has become one of the main POD approaches. However, the on-board GPS POD accuracy obviously relies on the accuracy of GPS orbit and clock products. Based on the zero-difference dynamic POD approach of SHORDE-III program, this paper shows the influence of GPS orbit and clock on the POD accuracy of LEO using real GRACE data and three types of IGS orbit products between 1 Aug. and 7 Aug. The results indicate that IGS final precise orbit product (igs) and rapid orbit product (igr) have the equal POD accuracy which is about 9.5cm, the POD accuracy using ultra-rapid orbit product (igu) is about 10.5cm which is a little worse than igs and igr; High-rate GPS clock products have an impact of about 1--6 cm on the POD accuracy of LEO.

Peng, D. J.; Wu, B.

2008-10-01

276

Orbit determination for Chang'E-2 lunar probe and evaluation of lunar gravity models

NASA Astrophysics Data System (ADS)

The Unified S-Band (USB) ranging/Doppler system and the Very Long Baseline Interferometry (VLBI) system as the ground tracking system jointly supported the lunar orbit capture of both Chang'E-2 (CE-2) and Chang'E-1 (CE-1) missions. The tracking system is also responsible for providing precise orbits for scientific data processing. New VLBI equipment and data processing strategies have been proposed based on CE-1 experiences and implemented for CE-2. In this work the role VLBI tracking data played was reassessed through precision orbit determination (POD) experiments for CE-2. Significant improvement in terms of both VLBI delay and delay rate data accuracy was achieved with the noise level of X-band band-width synthesis delay data reaching 0.2-0.3 ns. Short-arc orbit determination experiments showed that the combination of only 15 min's range and VLBI data was able to improve the accuracy of 3 h's orbit using range data only by a 1-1.5 order of magnitude, confirming a similar conclusion for CE-1. Moreover, because of the accuracy improvement, VLBI data was able to contribute to CE-2's long-arc POD especially in the along-track and orbital normal directions. Orbital accuracy was assessed through the orbital overlapping analysis (2 h arc overlapping for 18 h POD arc). Compared with about 100 m position error of CE-1's 200 km×200 km lunar orbit, for CE-2's 100 km×100 km lunar orbit, the position errors were better than 31 and 6 m in the radial direction, and for CE-2's 15 km×100 km orbit, the position errors were better than 45 and 12 m in the radial direction. In addition, in trying to analyze the Delta Differential One-Way Ranging (?DOR) experiments data we concluded that the accuracy of ?DOR delay was dramatically improved with the noise level better than 0.1 ns and systematic errors better calibrated, and the Short-arc POD tests with ?DOR data showed excellent results. Although unable to support the development of an independent lunar gravity model, the tracking data of CE-2 provided evaluations of different lunar gravity models through POD. It is found that for the 100 km×100 km lunar orbit, with a degree and order expansion up to 165, JPL's gravity model LP165P did not show noticeable improvement over Japan's SGM series models (100×100), but for the 15 km×100 km lunar orbit, a higher degree-order model can significantly improve the orbit accuracy.

Li, PeiJia; Hu, XiaoGong; Huang, Yong; Wang, GuangLi; Jiang, DongRong; Zhang, XiuZhong; Cao, JianFeng; Xin, Nan

2012-03-01

277

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

278

NASA Technical Reports Server (NTRS)

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

Gordon, Steven C.

1993-01-01

279

Nonlinear Estimation Theory Applied to the Interplanetary Orbit Determination Problem.

National Technical Information Service (NTIS)

The second order terms in a modified gaussian second order filter are investigated to determine their effect on the estimation accuracy. Conclusions indicate that the gain compensation term improves the estimation accuracy, when compared with the extended...

B. D. Tapley C. Y. Choe

1972-01-01

280

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

281

Precise orbit determination for NASA's earth observing system using GPS (Global Positioning System)

NASA Technical Reports Server (NTRS)

An application of a precision orbit determination technique for NASA's Earth Observing System (EOS) using the Global Positioning System (GPS) is described. This technique allows the geometric information from measurements of GPS carrier phase and P-code pseudo-range to be exploited while minimizing requirements for precision dynamical modeling. The method combines geometric and dynamic information to determine the spacecraft trajectory; the weight on the dynamic information is controlled by adjusting fictitious spacecraft accelerations in three dimensions which are treated as first order exponentially time correlated stochastic processes. By varying the time correlation and uncertainty of the stochastic accelerations, the technique can range from purely geometric to purely dynamic. Performance estimates for this technique as applied to the orbit geometry planned for the EOS platforms indicate that decimeter accuracies for EOS orbit position may be obtainable. The sensitivity of the predicted orbit uncertainties to model errors for station locations, nongravitational platform accelerations, and Earth gravity is also presented.

Williams, B. G.

1988-01-01

282

SPOT2 and TOPEX\\/Poseidon precise orbit determination from DORIS doppler tracking

The French earth observation satellite SPOT-2 has served as a testbed for precise orbit determination from DORIS doppler tracking in anticipation of the TOPEX\\/Poseidon mission. Using the most up-to-data gravity field model, JGM-2, a radial orbit accuracy of about 2–9 cm was achieved, with an rms of fit of the tracking data of about 0.64 mm\\/s. Furthermore, it was found

D. C. Kuijper; B. A. C. Ambrosius; K. F. Wakker

1995-01-01

283

SPOT2 and TOPEX\\/Poseidon precise orbit determination from DORIS doppler tracking

The French earth observation satellite SPOT-2 has served as a testbed for precise orbit determination from DORIS doppler tracking in anticipation of the TOPEX\\/Poseidon mission. Using the most up-to-date gravity field model, JGM-2, a radial orbit accuracy of about 2-9 cm was achieved, with an rms of fit of the tracking data of about 0.64 mm\\/s. Furthermore, it was found

D. C. Kuijper; B. A. C. Ambrosius; K. F. Wakker

1995-01-01

284

Results of the "Center for Orbit Determination in Europe" (CODE) during the IGS 1992 campaign.

NASA Astrophysics Data System (ADS)

During the 1992 IGS Campaign CODE operated as a processing center. The main emphasis thereby was the determination of precise orbits (global and European) using a dense network of about 12 sites in Europe and an additional set of about 10 globally distributed sites. In this paper the results of the three months experiment are presented: Global orbits, earth rotation parameters (ERP), and site coordinates.

Rothacher, M.; Beutler, G.; Brockmann, E.; Fankhauser, S.; Gurtner, W.; Springer, T.; Botton, S.; Mervart, L.; Wiget, A.; Wild, U.

285

NASA Technical Reports Server (NTRS)

A Global Positioning System (GPS) flight receiver provides a means of precisely determining orbits for satellites in low to moderate altitude orbits. Above 5000 km altitude, however, relatively few GPS satellites are visible. We present a new approach to orbit determination for satellites at higher altitudes. Modification of GPS ground receivers enables a beacon from the orbiter to be tracked simultaneously with GPS data. The orbit accuracy expected from this GPS-like tracking (GLT) technique in principle could be comparable to accuracies of GPS orbits. Present-day GPS orbit quality from a daily semi-automated analysis system at the Jet Propulsion Laboratory is at the 30 - 50 cm level: expected accuracies for orbiters with GLT are calculated to be in the few-meter range for altitudes up to 100000 km. For geosynchronous satellites, however, there are unique challenges due to geometrical limitations and to the lack of strong dynamical signature in tracking data. We examine two approaches for tracking Tracking and Data Relay Satellites (TDRS) geostationary orbiters. One uses GLT with a global network; the other relies on a small `connected element' ground network with a distributed clock for short baseline differential carrier phase (SB Delta Phi). In priciple, both could meet 50-m TDRS operational requirements. However there are practical difficulties with either pure GLT or SB Delta Phi tracking schemes for present-day TDRS satellites. We describe an experiment planned for late 1993 which will combine aspects of both GLT and SB Delta Phi to demonstrate a new approach for tracking TDRS which offers a number of operationally convenient and attractive features. The TDRS demo will in effect ba a proof of concept experiment for both the GLT and SB Delta Phi approaches to tracking spacecraft.

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

1993-01-01

286

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

287

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

288

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

289

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

290

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 {<}1 cm and 1 mm, respectively. Meanwhile, we show that the RMS of three-dimensional tidal geocenter variations is {<}6 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 {<}4 mm (3D RMS) and {<}2 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 6 hbox {mm}2 when tidal geocenter variations are treated inconsistently.

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

2014-04-01

291

Orbit determination accuracies using satellite-to-satellite tracking

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

292

Determination of the orbits of near-Earth asteroids from observations at the first opposition

NASA Astrophysics Data System (ADS)

Observations at the first opposition are used to determine the orbits of 16 near-Earth asteroids with two or more observed oppositions. The orbits are improved by the differential method. This paper considers two modifications of the improvement technique, which are compared to the classical method based on the principle of the least square method (LSM). The first modification uses the principle of least absolute deviations (LAD). In the second modification, the differences O - C (between the observed and calculated positions) are transformed to fit into a new coordinate system whereby the axes go parallel and perpendicular to the asteroid's apparent path (the modified differential method (MDM)). The orbits determined from one opposition by the classical LSM, LAD, and MDM are compared to a more accurate orbit calculated by the LSM from all the available oppositions. The calculations show that in 13 cases out of 16, the asteroid orbits calculated by LAD are more accurate than those calculated by the classical LSM. The improvement by the modified differential method, which includes the O - C transformation, does not produce any perceptible increase in accuracy when compared to the orbits calculated by the classical method.

Medvedev, Yu. D.

2011-10-01

293

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

294

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

295

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

296

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

297

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

298

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

299

Determination of Multiple Asteroid Orbits With a Genetic-Based Algorithm

NASA Astrophysics Data System (ADS)

Over the past decade, discoveries of multiple 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. We implemented a new approach presented in Vachier et al (A&A,2012), 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. 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. We will present additional mutual orbits determined using our method as they become available. This work has been supported by NASA grant NNX11AD62G

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

2012-10-01

300

The determinants of MNC subsidiary initiatives: implications for small business

Since the importance of the subsidiary's role continues to increase, a growing number of studies have focused on MNC subsidiary strategies. The aim of this study is to explore the determinants of a subsidiary's initiative. Based on the subsidiary research's classification provided by Birkinshaw and Hood, an integrated framework is developed to examine the influences of three groups of variables

Cher-Hung Tseng; Cher-Min Fong; Kuo-Hsien Su

2004-01-01

301

NASA Astrophysics Data System (ADS)

Absolute phase patterns for GNSS receiver and transmitter antennas are adopted in the processing standards of the International GNSS Service (IGS) since November 5, 2006 (GPS week 1400). The new antenna modeling is based on robot-calibrations for a number of terrestrial receiver antennas. Compatible antenna models are derived for the remaining terrestrial receiver antennas and the GNSS satellite antennas. However, consistent receiver antenna patterns are not available for many space missions equipped with onboard GPS sensor systems. Recently, nominal phase patterns obtained with a robotic measurement system in a field campaign have been made available for the antenna/chokering combination deployed on the CHAMP, GRACE, and TerraSAR-X satellites. We use the final product line from the Center for Orbit Determination in Europe (CODE: analysis center of the IGS) together with GPS data of the aforementioned low Earth orbiters (LEOs) for the year 2007 to assess the impact of nominal phase patterns on reduced-dynamic and kinematic LEO orbits computed by different and independent software packages (Bernese GPS software, GPS High-precision Orbit Determination Software Tools). In the actual spacecraft environment, however, pronounced phase center distortions may be encountered in addition due to multipath or cross-talk effects, which makes an additional in-flight calibration of LEO receiver antennas desirable. We compare methods for the in-flight derivation of empirical phase pattern corrections and discuss their relevance and applicability for precise orbit determination.

Jäggi, Adrian; Bock, Heike; Dach, Rolf; Montenbruck, Oliver; Hugentobler, Urs; Beutler, Gerhard

302

Federal Register 2010, 2011, 2012, 2013

...Investigation No. 337-TA-755] Certain Starter Motors and Alternators; Determination Not To Review an Initial Determination...United States after importation of certain starter motors and alternators that by reason of infringement of certain claims of...

2012-02-15

303

The Trajectory Analysis and Orbit Determination Program (TRACE) is a general purpose orbital analysis program. It was written and continues to be developed specifically to assist technical personnel in the analysis and design of satellite orbits and tracking systems. An input usage guide is presented that defines all input required to perform TRACE functions such as trajectory generation, data\\/observation generation,

W. D. Downs III; R. H. Prislin; D. C. Walker; R. J. Mercer

1974-01-01

304

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

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

305

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.

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

2014-01-01

306

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

307

Improvement Of The Ephemeris And Mass Of The Martian Moons From MEX Precise Orbit Determination

NASA Astrophysics Data System (ADS)

Because of the much larger eccentricity of the MEX orbit than that of the MGS orbit (eccentricity of 0.6 versus 0.01), MEX is more sensitive to the gravitational attraction of the Martian moons Phobos and Deimos. From the 2-way Doppler and range data provided by the MEX Radio Science (MaRS) experiment over the last three years, we perform MEX Precise Orbit Determination (POD) in order to improve both moons' ephemeris and mass. We use the GINS software developed by CNES and further adapted at ROB for planetary geodesy applications. We obtain an average precision of 20 meters or less on the MEX positioning around Mars. This represents an improvement by more than a factor 2 with respect to the MEX navigation orbit provided by the flight dynamics team of ESOC. Here, we show the impact of the improved MEX orbit on the Martian Moon ephemerides by using images of the moons taken by the camera (SRC) onboard MEX. We obtain estimates of the masses of Phobos and Deimos with formal errors that are comparable or better than previous estimates from MGS and Mars Odyssey. By using our accurate orbits of MEX, we also estimate the second order coefficients of the gravity field of Phobos, which can be used as a constraint on the internal mass distribution of Phobos.

Rosenblatt, P.; Lainey, V.; Le Maistre, S.; Marty, J.; Dehant, V.; Paetzold, M.; van Hoolst, T.; Hauesler, B.

2007-12-01

308

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

309

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

310

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

311

Determinants of Initiation Codon Selection during Translation in Mammalian Cells

Factors affecting translation of mRNA contribute to the complexity of eukaryotic proteomes. In some cases, translation of a particular mRNA can generate multiple proteins. However, the factors that determine whether ribosomes initiate translation from the first AUG codon in the transcript, from a downstream codon, or from multiple sites are not completely understood. Various mRNA properties, including AUG codon-accessibility and 5? leader length have been proposed as potential determinants that affect where ribosomes initiate translation. To explore this issue, we performed studies using synthetic mRNAs with two in-frame AUG codons?both in excellent context. Open reading frames initiating at AUG1 and AUG2 encode large and small isoforms of a reporter protein, respectively. Translation of such an mRNA in COS-7 cells was shown to be 5? cap-dependent and to occur efficiently from both AUG codons. AUG codon-accessibility was modified by using two different elements: an antisense locked nucleic acid oligonucleotide and an exon-junction complex. When either element was used to mask AUG1, the ratio of the proteins synthesized changed, favoring the smaller (AUG2-initiated) protein. In addition, we observed that increased leader length by itself changed the ratio of the proteins and favored initiation at AUG1. These observations demonstrate that initiation codon selection is affected by various factors, including AUG codon-accessibility and 5? leader length, and is not necessarily determined by the order of AUG codons (5??3?). The modulation of AUG codon accessibility may provide a powerful means of translation regulation in eukaryotic cells.

Matsuda, Daiki; Mauro, Vincent P.

2010-01-01

312

Orbital Evolution and Determination of Trans-Neptunian Binaries and Multiples

NASA Astrophysics Data System (ADS)

Numerous binary systems have been observed in the solar system beyond Neptune, including approximately one third of cold classical objects. These systems can be strongly perturbed by solar tides (Kozai cycles), dissipative body tides, spin-orbit interactions, and shape effects. Such perturbations can rapidly destabilize binary orbits, constraining both the allowed orbital solutions and the objects' physical properties. In addition, two hierarchical multiple systems are known, Pluto and (47171) 1999 TC36, and more will likely be discovered in the future. The hierarchical nature of these systems can cause rapid and complex orbital evolution over timescales fast enough to confuse a Keplerian fit. Precise modeling of these systems therefore requires a simulation that takes all these factors into account and which can easily interface with observational data. We are developing such a model by building an n-body simulator with shape-effects, torques, and body tides. In the process of fitting, it can constrain otherwise unobservable physical properties, such as shape, tidal dissipation, and masses for small satellites. In addition to better orbital determination, this model can also be used to test the stability of complex systems. Recent simulations have shown that a combination of Kozai cycles, body tides, and shape effects can dominate the evolution of trans-Neptunian binaries. This model can similarly determine which evolutionary paths can produce more complex trans-Neptunian systems.

Porter, Simon; Grundy, W.

2012-10-01

313

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

314

NASA Astrophysics Data System (ADS)

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

Flohrer, Tim; Beutler, Gerhard; Schildknecht, Thomas

315

Magnetospheric plasma analyzer: Initial three-spacecraft observations from geosynchronous orbit

The first three magnetospheric plasma analyzer (MPA) instruments have been returning data from geosynchronous orbit nearly continuously since late 1989, 1990, and 1991. These identical instruments provide for the first time simultaneous plasma observations from three widely spaced geosynchronous locations. The MPA instruments measure the three-dimensional velocity space distributions of both electrons and ions with energies between 1 eV\\/q and

D. J. McComas; S. J. Bame; B. L. Barraclough; J. R. Donart; R. C. Elphic; J. T. Gosling; M. B. Moldwin; K. R. Moore; M. F. Thomsen

1993-01-01

316

NASA Astrophysics Data System (ADS)

The article covers the outcome of the method for optimal filtering of measurements developed by the author and aimed at the determination of the time and place of reentry of the Phobos-Grunt spacecraft. So-called two-line elements (TLE) of the orbit of the American Space Surveillance System are used as measurements.

Nazarenko, A. I.

2013-12-01

317

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

318

Numerical comparison of discrete Kalman filter algorithms: Orbit Determination case study

Numerical characteristics of various Kalman filter algorithms are illustrated with a realistic orbit determination study. The case study of this paper highlights the numerical deficiencies of the conventional and stabilized Kalman algorithms, Computational errors associated with these algorithms are found to be so large as to obscure important mismodeling effects and thus cause misleading estimates of filter accuracy. The positive

Gerald J. Bierman; Catherine L. Thornton

1976-01-01

319

Numerical comparison of discrete Kalman filter algorithms - Orbit determination case study

Numerical characteristics of various Kalman filter algorithms are illustrated with a realistic orbit determination study. The case study of this paper highlights the numerical deficiencies of the conventional and stabilized Kalman algorithms. Computational errors associated with these algorithms are found to be so large as to obscure important mismodeling effects and thus cause misleading estimates of filter accuracy. The positive

G. J. Bierman; C. L. Thornton

1976-01-01

320

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

NASA Technical Reports Server (NTRS)

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

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

1976-01-01

321

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

322

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

323

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

324

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

325

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

326

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

327

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

328

A method of determining binary orbits by incorporating long-term observational data

NASA Astrophysics Data System (ADS)

Early ground based observations accumulated a large amount of long-term data about binary stellar systems. Compared with the data obtained by various present-day techniques, the early data have much lower precision. However, the span of the longer time interval makes these data still irreplaceable in certain astronomical researches. The present work shows that they are crucial in determining binary orbits with period longer than ~10 years, such as the G stars in the double and multiple systems annex of Hipparcos catalogue, and, a new combining method is developed in order to determine the above-mentioned orbits. There are two main steps. Firstly, by fitting IAD, we obtain many local minimum solutions. Then, the "best-fit" solution can be unambiguously selected by long-term observations. As an application, we revisit the binary stellar system "73Leo", of which there are only 7 usable long-term observational data and two different problematic orbit solutions. According to external analysis of the mass of secondary, we argue that the newly determined orbit and the component masses are reliable.

Ren, S. L.; Fu, Y. N.

2007-04-01

329

CHAMP and GRACE accelerometer calibration by GPS-based orbit determination

Current and planned Earth observation missions are equipped with highly sensitive accelerometers. Before using the data, the instrument has to be calibrated by determining scale and bias parameters for each axis. Here, the accelerometer measurements are used in a GPS-based reduced-dynamic orbit determination approach, replacing the non-gravitational force models, and nominally daily calibration parameters are estimated. Additional empirical accelerations are

Tom Van Helleputte; Eelco Doornbos; Pieter Visser

2009-01-01

330

NASA Astrophysics Data System (ADS)

A universal method of determining the orbits of newly discovered small bodies in the Solar System using their positional observations has been developed. The proposed method suggests determining geocentric distances of a small body by means of an exhaustive search for heliocentric orbital planes and subsequent determination of the distance between the observer and the points at which the chosen plane intersects with the vectors pointing to the object. Further, the remaining orbital elements are determined using the classical Gauss method after eliminating those heliocentric distances that have a fortiori low probabilities. The obtained sets of elements are used to determine the rms between the observed and calculated positions. The sets of elements with the least rms are considered to be most probable for newly discovered small bodies. Afterwards, these elements are improved using the differential method.

Bondarenko, Yu. S.; Vavilov, D. E.; Medvedev, Yu. D.

2014-05-01

331

An initial analysis of the data from the Polar Orbiting Geophysical (POGS) Satellite

NASA Technical Reports Server (NTRS)

The Polar Orbiting Geophysical Satellite (POGS) was launched in 1990 to measure the geomagnetic field. POGS data from selected magnetically quiet days was chosen, quality checked and deleted where thought to be erroneous. A time and position correction was applied. The resulting data was fit to a degree 13 spherical harmonic model. Evaluation of the quality of the data indicates that it is sufficient for definition of the low degree (approximately less than 8) portion of the geomagnetic field. Further correction of the data time and position may improve this quality.

Langel, R. A.; Sabaka, T. J.; Baldwin, R. T.

1991-01-01

332

Bilateral orbital myeloid sarcoma as initial manifestation of acute myeloid leukemia

Background Granulocytic sarcoma is a rare orbital complication of acute leukemia. It concerns primarily children under 10 years of age\\u000a suffering from primitive acute myeloid leukemia. The diagnosis is made by clinical examination, computed tomography and confirmed\\u000a by haematological investigations. The treatment approach is based on chemotherapy associated with intravenous steroid therapy.\\u000a \\u000a \\u000a \\u000a Case report We report the case of a 6-year-old girl who

Kamel Hmidi; Sonia Zaouali; Riadh Messaoud; Bahri Mahjoub; Wafa Ammari; Leila Bacha; Adnene Laatiri; Salah Jenzeri; Moncef Khairallah

2007-01-01

333

The status of YOHKOH in orbit - an introduction to the initial scientific results

NASA Astrophysics Data System (ADS)

The design and in-orbit function of the Yohkoh spacecraft and its four scientific instruments are described. The instruments include the Hard X-ray Telescope (HXT), the Soft X-ray Telescope (SXT), the Wide-Band Spectrometer (WBS), and the Bragg Crystal Spectrometers (BCS). The key feature of the Yohkoh is the combined use of the coaligned telescopes (HRT and SXT) and spectrometers (WBS and BCS) operating simultaneously, thus constituting a spaceborne solar observatory. The SXT has already taken hundreds of thousands of excellent pictures of active regions and of flares, and the HXT has obtained data concerning more than 200 major flares.

Ogawara, Yoshiaki; Acton, Loren W.; Bentley, Robert D.; Bruner, Marilyn E.; Culhane, J. Leonard; Hiei, Eijiro; Hirayama, Tadashi; Hudson, Hugh S.; Kosugi, Takeo; Lemen, James R.; Strong, Keith T.; Tsuneta, Saku; Uchida, Yutaka; Watanabe, Tetsuya; Yoshimori, Masato

1992-10-01

334

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

335

NASA Astrophysics Data System (ADS)

The Unit Vector Method (UVM) is an orbit determination method extensively applied. In this paper, the UVM and classical Differential Orbit Improvement (DOI) are compared, and a fusion method is given for the orbit determination with different kind data. Based on non-orthogonal decomposition of position and velocity vectors, an approximation scheme is constructed to calculate the state transition matrix. This method simplifies the calculation of the approximate state transition matrix, analyzes the convergence mechanism of the UVM, and makes clear the defect of weight strategy in UVM. Results of orbit the determination with simulating and real data show that this method has good numerical stability and rational weight distribution.

Chen, Wushen; Ma, Jingyuan; Zhang, Jing; Lu, Benkui

2010-03-01

336

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

Jung Hyun Jo

2002-01-01

337

TerraSAR-X precise orbit determination with real-time GPS ephemerides

NASA Astrophysics Data System (ADS)

TerraSAR-X is a German Synthetic Aperture Radar (SAR) satellite, which was launched in June 2007 from Baikonour. Its task is to acquire radar images of the Earth's surface. In order to locate the radar data takes precisely, the satellite is equipped with a high-quality dual-frequency GPS receiver -the Integrated Geodetic and Occultation Receiver (IGOR) provided by the GeoForschungsZentrum Potsdam (GFZ). Using GPS observations from the IGOR instrument in a reduced dynamic precise orbit determination (POD), the German Space Operations Center (DLR/GSOC) is computing rapid and science orbit products on a routine basis. The rapid orbit products arrive with a latency of about one hour after data reception with an accuracy of 10-20 cm. Science orbit products are computed with a latency of five days achieving an accuracy of about 5cm (3D-RMS). For active and future Earth observation missions, the availability of near real-time precise orbit information is becoming more and more important. Other applications of near real-time orbit products include the processing of GNSS radio occulation measurements for atmospheric sounding as well as altimeter measurements of ocean surface heights, which are nowadays employed in global weather and ocean circulation models with short latencies. For example after natural disasters it is necessary to evaluate the damage by satellite images as soon as possible. The latency and quality of POD results is mainly driven by the availability of precise GPS ephemerides. In order to have high-quality GPS ephemerides available at real-time, GSOC has developed the real-time clock estimation system RETICLE. The system receives NTRIP-data streams with GNSS observations from the global tracking network of IGS in real-time. Using the known station position, RETICLE estimates precise GPS satellite clock offsets and drifts based on the most recent available IGU predicted orbits. The clock offset estimates have an accuracy of better than 0.3 ns and are globally valid. The latency of the estimated clocks is approximately 7 seconds. Another limiting factor is the frequency of satellite downlinks and the latency of the data transfer from the ground station to the computation center. Therefore a near real-time scenario is examined in which the satellite has about one ground station contact per orbit or respectively one contact in 90 minutes. The results of the near real-time POD are evaluated in an internal consistency check and compared against the science orbit solution and laser ranging observations.

Wermuth, Martin; Hauschild, Andre; Montenbruck, Oliver; Kahle, Ralph

338

NASA Astrophysics Data System (ADS)

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

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

2010-07-01

339

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.

340

NASA Technical Reports Server (NTRS)

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

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

2011-01-01

341

Precise GLONASS orbit determination within the IGS/IGLOS Pilot Project

NASA Astrophysics Data System (ADS)

During the past 3.5 years, Russia has launched a number of new GLONASS satellites to renew step by step the whole space segment. 10 satellites are currently operational, while the new GLONASS-M satellite is still in commission phase. In parallel, the International GPS Service (IGS) established in 2000 a GLONASS Service Pilot Project (IGLOS) as a follow-on to the very successful International GLONASS Experiment (IGEX-98) that ended in April 1999. The IGLOS Pilot Project has a global network of over 40 tracking stations with dual-frequency GLONASS receivers, collocated with IGS GPS stations. As with the GPS data, the GLONASS data are collected continuously and archived in RINEX format at the IGS Global Data Centers. In addition, three of the satellites are routinely tracked by the International Laser Ranging Service, taking advantage of the retro-reflector array carried by each satellite. Three organizations, ESA/ESOC (European Space Operations Center, Germany), BKG (Bundesamt f. Kartographie u. Geodäsie, Germany) and CODE (University Berne, Switzerland), compute precise orbits from the receiver tracking data, while the Russian Mission Control Center computes orbits from the laser ranging data. The laser data provide a means to validate orbit determination modeling and to investigate orbit residuals. These 4 independent orbits, which are consistent at the 10-15cm level, are used by the IGLOS Analysis Coordinator to compute one combined IGLOS orbit for each satellite. The IGLOS project is a working model of a 2-system GNSS. Time standardization, reference frames and file formats have been addressed to handle GPS and GLONASS data in the same operations. The combined systems contain over 36 satellites, which can be exploited for many applications. In this context time transfer, real-time navigation, and atmospheric studies are valid examples which can benefit from the additional data that GLONASS provides. Finally, taking into consideration the upcoming GALILEO system, IGLOS can pave the way for handling data from a multi-system GNSS.

Weber, R.; Fragner, E.; Slater, J. A.; Habrich, H.; Glotov, V.; Romero, I.; Schaer, S.

342

NASA Astrophysics Data System (ADS)

The problem arose with regard to a project of a space mission to the vicinity of the collinear libration point L2 in the Sun - Earth system with a close flyby near the Moon (project "Relict-2"). At the initial part of the space trajectory the spacecraft performs 2.5 revolutions around the Earth in the orbit with a perigee close to the Earth surface and an apogee in the vicinity of the Moon's orbit. The computational time of PC, required for calculating such a trajectory by numerical integration within a given accuracy and with account for a complicated gravity effect of the Earth, proves to be large. Solving boundary control problems in real time needs multiple computations of such trajectories. In view of this, the problem of increasing the computational speed becomes rather urgent. A technique of splitting the trajectory into segments is proposed to solve this problem.

Lidov, M. L.; Teslenko, N. M.

1994-12-01

343

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

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

344

Assessing attitude error of FORMOSAT-3/COSMIC satellites and its impact on orbit determination

NASA Astrophysics Data System (ADS)

An attitude determination and control system (ADCS) is critical to satellite attitude maneuvers and to the coordinate transformation from the inertial frame to the spacecraft frame. This paper shows specific sensors in the ADCS of the satellite mission FORMOSAT-3/COSMIC (F3/C) and the impact of the ADCS quality on orbit accuracy. The selection of main POD antenna depends on the beta angles of the different F3/C satellites (for FM2 and FM4) during the inflight phase. In particular, under the eclipse, alternative attitude sensors are activated to replace the Sun sensors, and such a sensor change leads to anomalous GPS phase residuals and a degraded orbit accuracy. Since the nominal attitude serves as a reference for ADCS, the 3-dimensional attitude-induced errors in reduced dynamic orbits over selected days in 2010 show 9.35, 10.78, 4.97, 5.48, 7.18, and 6.89 cm for FM1-FM6. Besides, the 3-dimensional velocity errors induced by the attitude effect are 0.10, 0.10, 0.07, 0.08, 0.09, and 0.10 for FM1-FM6. We analyze the quality of the observed attitude transformation matrix of F3/C and its impact on kinematic orbit determination. With 249 days of GPS in 2008, the analysis leads to the following averaged 3-dimensional attitude-induced orbit errors: 2.72, 2.62, 2.37, 1.90, 1.70, and 1.99 cm for satellites FM1-FM6. Critical suggestions of geodetic payloads for the follow-on mission of F3/C are presented based on the current result.

Tseng, Tzu-Pang; Hwang, Cheinway; Yang, Shan Kuo

2012-05-01

345

Estimation strategies for orbit determination of applications satellites. [using covariance analysis

NASA Technical Reports Server (NTRS)

A procedure for applying covariance analysis to determine the most efficient estimation strategy for satisfying the stringent mission requirements of long arc orbit determination of applications satellites is presented. The procedure is applied to the problem of satisfying mission requirements with respect to altitude determination of GEOS-C. It is shown that requirements are met when twelve dominant geopotential coefficients are estimated along with satellite state. This application of covariance analysis is general and can be applied to future applications satellites. Recommendations for future studies are also given.

Argentiero, P.; Lynn, J. J.

1974-01-01

346

40 CFR 142.11 - Initial determination of primary enforcement responsibility.

Code of Federal Regulations, 2013 CFR

...Initial determination of primary enforcement responsibility. 142.11 Section...REGULATIONS IMPLEMENTATION Primary Enforcement Responsibility Â§ 142.11 Initial determination of primary enforcement responsibility. (a) A...

2013-07-01

347

Orbit Determination for the Be/X-Ray Transient EXO 2030+375

NASA Technical Reports Server (NTRS)

The Be/X-ray binary transient pulsar EXO 2030+375 has been observed during twenty-two outbursts over four years (1991-1994) using the large area detectors (LADs) of the Burst and Transient Source Experiment (BATSE) on the Compton Gamma-Ray Observatory (CGRO). Thirteen outbursts between 1992 February and 1993 August occurred regularly at -46 day intervals, close to the orbital period determined using EXOSAT data. EXOSAT discovered this pulsar during, a "giant" outburst in 1985 May. All BATSE outbursts were "normal" type. Pulse phases derived from the thirteen consecutive outbursts were fit to two different models to determine a binary orbit. A summary of the results are presented here.

Stollberg, Mark T.; Finger, Mark H.; Wilson, Robert B.; Scott, Matthew; Crary, David J.; Paciesas, William S.

1999-01-01

348

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

349

Orbit determination and gravitational field accuracy for a Mercury transponder satellite

NASA Technical Reports Server (NTRS)

Covariance studies were performed to investigate the orbit determination problem for a small transponder satellite in a nearly circular polar orbit with 4-hour period around Mercury. With X band and Ka band Doppler and range measurements, the analysis indicates that the gravitational field through degree and order 10 can be solved for from as few as 40 separate 8-hour arcs of tracking data. In addition, the earth-Mercury distance can be determined during each ranging period with about 6-cm accuracy. The expected geoid accuracy is 10 cm up through degree 5, and 1 m through degree 8. The main error sources were the geocentric range measurement error, the uncertainties in higher degree gravity field terms, which were not solved for, and the solar radiation pressure uncertainty.

Vincent, Mark A.; Bender, Pater L.

1990-01-01

350

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

351

The Precise orbital determination of Earth satellites: a tool for investigating the atmosphere ?

NASA Astrophysics Data System (ADS)

In the present decade Earth s explorer missions like CHAMP GRACE and GOCE are going to dramatically improve the knowledge of the Earth s gravity field Such improvement has lowered indeed the threshold of gravity field uncertainties which affects the orbital motion of Earth satellites Previously it was demonstrated that subtle effects due to Earth tides atmospheric drag solar radiation pressure and general relativity which before were choked by the gravity field uncertainties now prevails on classical gravity field uncertainties Thus with the present work we try to prove that the tremendous improvement of the gravity field models could make feasibile the use of precise orbit determination of Earth satellites as a tool for sensing a global changes of some key atmosphere parameters like refractivity and extinction Furthermore the huge number of running Earth s satellites and combinations of their orbital parameters namely the nodes in a gravity field free fashion GF-free can magnify the solar radiation pressure acting on high Earth s Satellites like GPS or Etalon satellites and its smooth modulation through the Earth s atmosphere penumbra We would remind that The GF-free technique is able to cancel out with n satellite orbital parameters the first n-1 even zonal harmonics of the gravity field We outline that the GF-free technique was before widely applied for measuring subtle general relativistic effects like the gravitomagnetic field

Vespe, F.; D'Alessandro, E.

352

Chang’E-1 precision orbit determination and lunar gravity field solution

NASA Astrophysics Data System (ADS)

In this paper we present results assessing the role of Very Long Baseline Interferometry (VLBI) tracking data through precision orbit determination (POD) during the check-out phase for Chang'E-1, and the lunar gravity field solution CEGM-01 based on the orbital tracking data acquired during the nominal phase of the mission. The POD of Chang'E-1 is performed using S-band two-way Range and Range Rate (R&RR) data, together with VLBI delay and delay rate observations. The role of the VLBI data in the POD of Chang'E-1 is analyzed, and the resulting orbital accuracies are estimated for different solution strategies. The final orbital accuracies proved that the VLBI tracking data can improve the Chang'E-1 POD significantly. Consequently, CEGM-01 based on six-month tracking data during Chang'E-1 nominal mission phase is presented, and the accuracy of the model is assessed by means of the gravity field power spectrum, admittance and coherence between gravity and topography, lunar surface gravity anomaly and POD for both Chang'E-1 and Lunar Prospector (LP). Our analysis indicates that CEGM-01 has significant improvements over a prior model (i.e. GLGM-2), and shows the potential of Chang'E-1 tracking data in high resolution lunar gravity field model solution by combining with SELENE and LP tracking data.

Jianguo, Yan; Jinsong, Ping; Fei, Li; Jianfeng, Cao; Qian, Huang; Lihe, Fung

2010-07-01

353

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

354

One-Centimeter Orbit Determination for Jason1: New GPS-Based Strategies

The U.S.\\/French Jason-1 satellite is carrying a state-of-the-art GPS receiver to support precise orbit determination (POD) requirements. The performance of the Jason-1 “BlackJack” GPS receiver was strongly reflected in early POD results from the mission, enabling radial accuracies of 1–2 cm soon after the satellite's 2001 launch. We have made further advances in the GPS-based POD for Jason-1, most notably

BRUCE HAINES; YOAZ BAR-SEVER; WILLY BERTIGER; SHAILEN DESAI; PASCAL WILLIS

2004-01-01

355

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

NASA Technical Reports Server (NTRS)

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

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

2010-01-01

356

Fast orbit determination of space debris with the use of Pulkovo AMP-method

The new Apparent Motion Parameters method (the AMP-method) developed by Dr.A.Kiselev and O.Bykov at Pulkovo observatory can be used for an express orbit determination of any artificial Near Earth Object having several (5 or more) accurate topocentric positions along a supershort celestial arc. One can obtain these crowded positions with a modern astronomical CCD-technique during several minutes of observations. The

O. P. Bykov; A. V. Shkondin

1997-01-01

357

CHAMP and GRACE accelerometer calibration by GPS-based orbit determination

NASA Astrophysics Data System (ADS)

Current and planned Earth observation missions are equipped with highly sensitive accelerometers. Before using the data, the instrument has to be calibrated by determining scale and bias parameters for each axis. Here, the accelerometer measurements are used in a GPS-based reduced-dynamic orbit determination approach, replacing the non-gravitational force models, and nominally daily calibration parameters are estimated. Additional empirical accelerations are estimated to account for deficiencies in the applied force models. This method is applied to 5 years of CHAMP and GRACE data, resulting in an orbit precision at the level of a few centimeters. In along-track direction the calibration parameters can be estimated freely, scale factors of 0.96 ± 0.014 and 0.95 ± 0.015 are obtained for GRACE A and B, and 0.85 ± 0.024 for CHAMP. A constant scale factor results in the smoothest bias series, with clear trends and occasional jumps. In radial and cross-track direction tight constraints to a priori biases have to be applied. Furthermore, the determined orbits are analyzed with respect to reference trajectories, and SLR, phase and KBR residuals are presented.

Helleputte, Tom Van; Doornbos, Eelco; Visser, Pieter

2009-06-01

358

NASA Technical Reports Server (NTRS)

The visual orbit of the spectroscopic binary Alpha And is determined independently of spectroscopic data using the Mark III Stellar Interferometer. Observations of Alpha And in 1988 and 1989 clearly demonstrate submilliarcsecond measurement precision at optical wavelengths. All of the orbital elements of Alpha And are calculated utilizing observations from the stellar interferometer only and are in excellent agreement with the spectroscopic results. However, three of these elements can only be obtained from interferometric data. Using both interferometric and spectroscopic observations, the definitive orbital elements are determined including angular semimajor axis, inclination, position angle of ascending node, longitude of periastron, period eccentricity, and epoch of periastron passage. In addition, the magnitude difference between the two components is measured, yielding delta-m = 1.82 +/- 0.04 mag at 800 nm and delta-m = 1.99 +/- 0.04 mag at 550 nm. Incorporating photometric observations, the color indices between 550 nm and 800 nm for the primary and the companion are determined as -0.11 +/- 0.03 mag +0.07 +/- 0.05 mag, respectively.

Pan, Xiaopei; Shao, Michael; Colavita, M. M.; Armstrong, J. T.; Mozurkewich, David; Vivekanand, Maddali; Denison, Craig S.; Simon, Richard S.; Johnston, Kenneth J.

1992-01-01

359

Local-scaling transformations are used in the present work to obtain accurate Kohn--Sham 1[ital s] and 2[ital s] orbitals for the beryllium atom by means of a density-constrained variation of the single-determinant kinetic energy functional. An analytic representation of these Kohn--Sham orbitals is given and the quality of the different types of orbitals generated is discussed with particular reference to their

Eduardo V. Ludeña; Jorge Maldonado; Roberto López-Boada; Toshikatsu Koga; Eugene S. Kryachko

1995-01-01

360

Local-scaling transformations are used in the present work to obtain accurate Kohn–Sham 1s and 2s orbitals for the beryllium atom by means of a density-constrained variation of the single-determinant kinetic energy functional. An analytic representation of these Kohn–Sham orbitals is given and the quality of the different types of orbitals generated is discussed with particular reference to their kinetic energy

Jorge Maldonado; Roberto Lo´pez-Boada; Toshikatsu Koga; Eugene S. Kryachko

1995-01-01

361

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

362

NASA Technical Reports Server (NTRS)

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

Chato, David J.

1991-01-01

363

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

364

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

365

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

366

DPOD2005: An extension of ITRF2005 for Precise Orbit Determination

NASA Astrophysics Data System (ADS)

For Precise Orbit Determination of altimetry missions, we have computed a data set of DORIS station coordinates defined for specific time intervals called DPOD2005. This terrestrial reference set is an extension of ITRF2005. However, it includes all new DORIS stations and is more reliable, as we disregard stations with large velocity formal errors as they could contaminate POD computations in the near future. About 1/4 of the station coordinates need to be defined as they do not appear in the original ITRF2005 realization. These results were verified with available DORIS and GPS results, as the integrity of DPOD2005 is almost as critical as its accuracy. Besides station coordinates and velocities, we also provide additional information such as periods for which DORIS data should be disregarded for specific DORIS stations, and epochs of coordinate and velocity discontinuities (related to either geophysical events, equipment problem or human intervention). The DPOD model was tested for orbit determination for TOPEX/Poseidon (T/P), Jason-1 and Jason-2. Test results show DPOD2005 offers improvement over the original ITRF2005, improvement that rapidly and significantly increases after 2005. Improvement is also significant for the early T/P cycles indicating improved station velocities in the DPOD2005 model and a more complete station set. Following 2005 the radial accuracy and centering of the ITRF2005-original orbits rapidly degrades due to station loss.

Willis, P.; Ries, J. C.; Zelensky, N. P.; Soudarin, L.; Fagard, H.; Pavlis, E. C.; Lemoine, F. G.

2009-09-01

367

NASA Astrophysics Data System (ADS)

Kinematic precise orbit determination (POD) is independent of satellite dynamics (e.g., Earth gravity field, atmospheric drag, solar radiation pressure, etc.). It is the distinctive approach of space-borne GPS technique, and well suited for orbit determination of Low Earth orbiting (LEO) satellites which are strongly perturbed by atmosphere. Firstly, an algorithm of kinematic POD is developed by using the zero-difference space-borne dual-frequency GPS measurements in this paper. And then, how to pre-process the space-borne dual-frequency GPS data and how to set the estimated parameters of kinematic POD are discussed in detail. Finally, the observational data from GRACE (Gravity Recovery And Climate Experiment) satellites covering the whole month of February 2008 are employed to validate the effectiveness and reliability of the method introduced in this paper. It is demonstrated that kinematic POD reaches an accuracy of about 5 cm (with respect to satellite laser ranging), which is at the same level of accuracy as dynamic and reduced-dynamic POD.

Peng, D. J.; Wu, B.

2011-11-01

368

Precise Orbit Determination of LEO Satellite Using Dual-Frequency GPS Data

NASA Astrophysics Data System (ADS)

KOrea Multi-purpose SATellite (KOMPSAT)-5 will be launched at 550km altitude in 2010. Accurate satellite position (20 cm) and velocity (0.03 cm/s) are required to treat highly precise Synthetic Aperture Radar (SAR) image processing. Ionosphere delay was eliminated using dual frequency GPS data and double differenced GPS measurement removed common clock errors of both GPS satellites and receiver. SAC-C carrier phase data with 0.1 Hz sampling rate was used to achieve precise orbit determination (POD) with ETRI GNSS Precise Orbit Determination (EGPOD) software, which was developed by ETRI. Dynamic model approach was used and satellite's position, velocity, and the coefficients of solar radiation pressure and drag were adjusted once per arc using Batch Least Square Estimator (BLSE) filter. Empirical accelerations for sinusoidal radial, along-track, and cross track terms were also estimated once per revolution for unmodeled dynamics. Additionally piece-wise constant acceleration for cross-track direction was estimated once per arc. The performance of POD was validated by comparing with JPL's Precise Orbit Ephemeris (POE).

Hwang, Yoola; Lee, Byoung-Sun; Kim, Jaehoon; Yoon, Jae-Cheol

2009-06-01

369

Preliminary results of the satellite orbit determination of Mariner Mars 1971.

NASA Technical Reports Server (NTRS)

The preflight planning and real-time experience relating to the navigation of the first artificial satellite placed about a distant planet is presented. Results of determining the orbit of Mariner 9 are presented and contrasted against the preflight simulation test results. It is concluded that the position of Mariner 9 was located to 40 km before coefficients of the gravity field of Mars were estimated. The planet Mars has been found to be 3 to 4 times gravitationally rougher than expected, with the dominant features, the 2nd order tesserals C22 and S22, causing the orbital period of Mariner 9 to oscillate with an amplitude of 40 seconds and a wavelength of 19.5 days. The direction of the Mars spin axis has been relocated from the Camichel-Burton value by 1/2 degree.

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

1972-01-01

370

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

371

COS NUV Initial On-Orbit Turn-On and Recovery after Anomalous Shutdown

NASA Astrophysics Data System (ADS)

This proposal is designed for the initial turn-on of the COS NUV MAMA detector. The same procedure may later be used to recover the detector after an anomalous shutdown. Anomalous shutdowns can occur as a result of bright object violations which trigger the Bright Scene Detection or Software Global Monitor. Anomalous shutdowns can also occur as a result of MAMA hardware problems. The Initial MAMA turn-on consists of three tests: a signal processing electronics check; a slow high voltage ramp-up to an intermediate voltage; and a slow high voltage ramp-up to the full operating voltage. During each of the two high voltage ramp-ups, diagnostics are performed during a dark time-tag exposure. The turn-on is followed by a MAMA Fold Analysis Test. The complete sequence is contained in visits 1 through 4. If a second execution is required during cycle 17, visits 5 through 8 will be run and another proposal prepared for possible future occurrences. Supports Activities COS-04 and COS-07;

Welty, Alan

2008-07-01

372

We develop and test a methodology to determine the relativistic electron phase space density distribution in the vicinity of geostationary orbit by making use of the pitch-angle resolved energetic electron data from three Los Alamos National Laboratory geosynchronous Synchronous Orbit Particle Analyzer instruments and magnetic field measurements from two GOES satellites. Owing to the Earth's dipole tilt and drift shell

Y. Chen; R. H. W. Friedel; G. D. Reeves; T. G. Onsager; M. F. Thomsen

2005-01-01

373

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

374

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

375

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

376

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

377

BATSE Observations and Orbit Determination of the Be/X-Ray Transient EXO 2030+375

NASA Technical Reports Server (NTRS)

The Be/X-ray binary transient pulsar EXO 2030+375 (P(sub s) approx equal 42 s) has been observed with the large area detectors (LADs) of the Burst and Transient Source Experiment (BATSE) on the Compton Gamma-Ray Observatory (CGRO). Beginning in May 1991, twenty-two outbursts were observed over four years. Thirteen outbursts between February 1992 and August 1993 occurred consecutively at intervals of approx equal 46 days, close to the orbital period determined by Parmar et al. (1989) using EXOSAT data. The pulse profiles from the BATSE data are double-peaked and show no significant energy or luminosity dependence, unlike the EXOSAT observations of May-August 1985. An exponential model was used to fit the observed hard X-ray energy spectra from the thirteen consecutive outbursts. When EXOSAT discovered this pulsar during a giant outburst in May 1985, the X-ray luminosity peaked at L(sub x) = 1.0 x 10(esp 38) erg/ s (1-20 keV), assuming a 5 kpc distance to the source. The BATSE outbursts are found to be weaker 0.3 x 10(exp 37) less than or equal to L(sub x)(I-20 keV) less than or equal to 3.0 x 10(exp 37) erg/ s after extrapolating the observed flux (20-50 keV) to the EXOSAT energy band. Pulse phases derived from the thirteen outbursts were fit to two different models to determine a binary orbit. The new orbit is used to estimate 95% confidence limits for the mean peak spin frequency change during the out- bursts observed with BATSE. This, and the mean peak flux, are compared to the spin-up rates and fluxes determined by EXOSAT from the 1985 giant outburst, where disk accretion was thought to have occurred. It is unclear if these normal outbursts were driven by wind or disk accretion.

Strollberg, Mark T.; Finger, Mark H.; Wilson, Robert B.; Scott, D. Matthew; Crary, David J.; Paciesas, William S.

1998-01-01

378

Precision Time Transfer and Obit Determination Using Laser Ranging to Lunar Reconnaissance Orbiter

NASA Astrophysics Data System (ADS)

Since the commissioning of LRO in June, 2009, one-way laser ranging (LR) to Lunar Reconnaissance Orbiter (LRO) has been conducted successfully from NASA's Next Generation Satellite Laser Ranging System (NGSLR) at Goddard Geophysical and Astronomical observatory (GGAO) in Greenbelt, Maryland. With the support of the International Laser Ranging Service (ILRS), ten international satellite laser ranging (SLR) ground stations have participated in this experiment and over 1200 hours of ranging data have been collected. In addition to supplementing the precision orbit determination (POD) of LRO, LR is able to perform time transfer between the ground station and the spacecraft clocks. The LRO clock oscillator is stable to 1 part in 10^{12} over several hours, and as stable for much longer periods after correcting for a long-term drift rate and an aging rate. With a precisely-determined LRO ephemeris, the oscillator-determined laser pulse receive time can be differenced with ground station clock transmit times using H-maser and GPS-steered Rb oscillators as references. Simultaneous ranging to LRO among 2, 3, or 4 ground stations has made it possible for relative time transfer among the participating LR stations. Results have shown about 100 ns difference between some LR stations and the primary NGSLR station. At present, the time transfer accuracy is limited to 100 ns at NGSLR. However, an All-View GPS receiver has been installed, which, in combination with a H-maser, is expected to improve the accuracy to 1 ns r.m.s. at NGSLR. Results of new ranging and time transfer experiments using the new time base will be reported. The ability to use LR for time transfer validates the selection of a commercially-supplied, oven-controlled crystal oscillator on board LRO for one-way laser ranging.The increased clock accuracy also provides stronger orbit constraints for LRO POD. The improvements due to including LR data in the LRO POD will be presented.

Mao, D.; Barker, M. K.; Clarke, C. B.; Golder, J. E.; Hoffman, E.; Horvath, J. E.; Mazarico, E.; Mcgarry, J.; Neumann, G. A.; Torrence, M. H.; Rowlands, D. D.; Skillman, D.; Smith, D. E.; Sun, X.; Zuber, M. T.

2011-12-01

379

Use of regularization method in the determination of ring parameters and orbit correction

We discuss applying the regularization method of Tikhonov to the solution of inverse problems arising in accelerator operations. This approach has been successfully used for orbit correction on the NSLS storage rings, and is presently being applied to the determination of betatron functions and phases from the measured response matrix. The inverse problem of differential equation often leads to a set of integral equations of the first kind which are ill-conditioned. The regularization method is used to combat the ill-posedness.

Tang, Y.N.; Krinsky, S.

1993-01-01

380

Use of regularization method in the determination of ring parameters and orbit correction

We discuss applying the regularization method of Tikhonov to the solution of inverse problems arising in accelerator operations. This approach has been successfully used for orbit correction on the NSLS storage rings, and is presently being applied to the determination of betatron functions and phases from the measured response matrix. The inverse problem of differential equation often leads to a set of integral equations of the first kind which are ill-conditioned. The regularization method is used to combat the ill-posedness.

Tang, Y.N.; Krinsky, S.

1993-07-01

381

NASA Astrophysics Data System (ADS)

A two-way adaptive Kalman filter is proposed by combining a two-way filter with an adaptive filter for orbit determination of a maneuvered GEO satellite. A method of using Newton's high-resolution differential formula and polynomial fitting for modeling the thrust force of a maneuvered GEO satellite is developed. The adaptive factor, which balances the contributions of the measurements and the dynamic model information, is determined by using a two-segment function and predicted residual statistics. Simulations with a maneuvered GEO satellite tracked by the Chinese ground tracking network were conducted to verify the performance of the proposed orbit determination technique and the method of thrust force modeling. The results show that refining the thrust force model is beneficial for the orbit determination of a maneuvered GEO satellite; the two-way adaptive Kalman filter can efficiently control the influence of the dynamic model errors on the orbit state estimate.

Xu, TianHe; He, KaiFei; Xu, GuoChang

2012-04-01

382

The use of Orbital Electronegativities in the interpretation of NQR results for various halides is discussed, and an attempt to determine the amount of d hybridization in s and p bonding is made. The ionic characters are assessed.

M. A. Whitehead; H. H. Jaffé

1963-01-01

383

Statistical ranging of orbits for trans-neptunian objects

We consider initial determination of orbits for trans-neptunian objects (TNOs), a topical theme because of the rapidly growing TNO population and the challenges in recovering lost TNOs. We apply the method of initial phase-space ranging of orbits to the poorly observed TNOs. The rigorous a posteriori probability density of the TNO orbital elements is examined using a Monte Carlo technique

J. Virtanen; K. Muinonen; E. Bowell

2002-01-01

384

Orbit correction in an orbit separated cyclotron

NASA Astrophysics Data System (ADS)

The orbit separated proton cyclotron (OSC) described in [1] differs in concept from that of a separated orbit cyclotron (SOC) [2]. Synchronous acceleration in an OSC is based on harmonic number jumps and orbit length adjustments via reverse bending. Four-turn acceleration in the OSC enables it to have four times fewer cryogenic-cavity systems than in a superconducting linac of the same high beam power and energy range. Initial OSC studies identified a progressive distortion of the spiral beam orbits by the off-axis, transverse deflecting fields in its accelerating cavities. Compensation of the effects of these fields involves the repeated use of a cavity field map, in a 3-D linac tracking code, to determine the modified arc bends required for the OSC ring. Subsequent tracking studies confirm the compensation scheme and show low emittance growth in acceleration.

Plostinar, C.; Rees, G. H.

2014-04-01

385

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

386

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

387

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.

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

2011-01-01

388

Translation of picornavirus RNA is initiated after ribosomal binding to an internal ribosomal entry site (IRES) within the 5' untranslated region. We have reconstituted IRES-mediated initiation on encephalomyocarditis virus RNA from purified components and used primer extension analysis to confirm the fidelity of 48S preinitiation complex formation. Eukaryotic initiation factor 2 (eIF2), eIF3, and eIF4F were required for initiation; eIF4B and to a lesser extent the pyrimidine tract-binding protein stimulated this process. We show that eIF4F binds to the IRES in a novel cap-independent manner and suggest that cap- and IRES-dependent initiation mechanisms utilize different modes of interaction with this factor to promote ribosomal attachment to mRNA.

Pestova, T V; Hellen, C U; Shatsky, I N

1996-01-01

389

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

390

20 CFR 663.515 - What is the process for initial determination of provider eligibility?

Code of Federal Regulations, 2013 CFR

...process for initial determination of provider eligibility? 663.515 Section...INVESTMENT ACT Eligible Training Providers Â§ 663.515 What is the process for initial determination of provider eligibility? (a) To be...

2013-04-01

391

NASA Astrophysics Data System (ADS)

Lobate debris aprons, known to be geomorphic landform indicators of the presence of ground ice, are of special interest for future missions devoted to the research of water on Mars. Lobate debris aprons in fretted terrains of Deuteronilus and Protonilus Mensae (35°-50°N) show typical convex shapes interpreted to be the result of viscous deformation. At the scale of Mars Orbiter Camera (MOC) high-resolution images the surface of these debris aprons shows complex patterns with small pits and buttes. These patterns can be explained by the mantling of dust, the accumulation of interstitial ice, and the subsequent removal of ice by sublimation. The sublimation of the ground ice is especially initiated and accelerated by subsurface heterogeneities like fractures. Theoretical quantification of sublimation rates therefore minimizes sublimation, which is not a homogeneous process, at least over the landforms studied. Crater counts show that the sublimation occurred in the last tens of millions of years up to the recent past. In the point of view of future searching of subsurface ice, only surface layers are submitted to sublimation favoring the conservation of ground ice in deeper layers since the formation of the landform. The geophysical survey of lobate debris aprons would give interesting insights into the subsurface distribution of ice and its seasonal variations, especially in order to measure current sublimation of ground ice.

Mangold, N.

2003-01-01

392

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

393

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

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

394

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

395

Orbit Determination and Quality Assessment Using SELENE Tracking Data and Results

On September 14, 2007, the SELENE (KAGUYA) spacecraft were launched from Tanegashima Space Center in Japan. SELENE consists of three satellites: a main orbiter in a 100 km by 100 km circular, polar orbit, and two small subsatellites in 100 km by 2400 km (Rstar) and 100 km by 800 km (Vstar) elliptical, polar orbits. Until now, tracking of lunar

Sander Goossens; Koji Matsumoto; Yoshiaki Ishihara; Qinghui Liu; Fuyuhiko Kikuchi; Hirotomo Noda; Noriyuki Namiki; Takahiro Iwata

2008-01-01

396

Federal Register 2010, 2011, 2012, 2013

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

2013-07-25

397

NASA Astrophysics Data System (ADS)

In the case of that the parameters of orbit plane (i,?) are given, a method for preliminary orbit determination is presented for range data of single station and single arc with the principle of Unit-Vector-Method(UVM). Especially, if the angular data are not available or the accuracy of angular data is much lower than that of range data, this method is efficient and valuable.

Zhang, J.; Ma, J. Y.; Lu, B. K.; Fu, M. H.; Zou, H. Z.

2005-10-01

398

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

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Will we mail you a notice of the initial determination...Determinations Â§ 408.1005 Will we mail you a notice of the initial determination? (a) We will mail a written notice of the initial...

2013-04-01

399

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

400

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

401

Complete determination of molecular orbitals by measurement of phase symmetry and electron density.

Several experimental methods allow measuring the spatial probability density of electrons in atoms, molecules and solids, that is, the absolute square of the respective single-particle wave function. But it is an intrinsic problem of the measurement process that the information about the phase is generally lost during the experiment. The symmetry of this phase, however, is a crucial parameter for the knowledge of the full orbital information in real space. Here, we report on a key experiment that demonstrates that the phase symmetry can be derived from a strictly experimental approach from the circular dichroism in the angular distribution of photoelectrons. In combination with the electron density derived from the same experiment, the full quantum mechanical wave function can thus be determined experimentally. PMID:24910256

Wießner, M; Hauschild, D; Sauer, C; Feyer, V; Schöll, A; Reinert, F

2014-01-01

402

Applications of singular value analysis and partial-step algorithm for nonlinear orbit determination

NASA Astrophysics Data System (ADS)

An adaptive method in which cruise and nonlinear orbit determination problems can be solved using a single program is presented. It involves singular value decomposition augmented with an extended partial step algorithm. The extended partial step algorithm constrains the size of the correction to the spacecraft state and other solve-for parameters. The correction is controlled by an a priori covariance and a user-supplied bounds parameter. The extended partial step method is an extension of the update portion of the singular value decomposition algorithm. It thus preserves the numerical stability of the singular value decomposition method, while extending the region over which it converges. In linear cases, this method reduces to the singular value decomposition algorithm with the full rank solution. Two examples are presented to illustrate the method's utility.

Ryne, Mark S.; Wang, Tseng-Chan

403

Aperture determination of RHIC92 from randomly generated initial coordinates

Results obtained by tracking 100 particles for 1,000 turns when initial coordinates are selected randomly, with the requirement that the total emittance be constant, are compared to results from 1,000-turn and 10{sup 6}-turn runs when initial coordinates satisfy {epsilon}{sub x}(i) = {epsilon}{sub y}(i) and X{sub i}{prime} = Y{sub i}{prime} = 0. For studies of ten distributions of magnetic field errors, the 100-particle results given apertures equivalent to those from 10{sup 6}-turn runs, have an aperture distribution of considerably less width, and yet require only one tenth the computer time.

Dell, G.F.

1992-12-31

404

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 adjuste