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At least 523 records · Page 29

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DOE OSTI2021

Gravity Probe Spin: Prospects for measuring general-relativistic precession of intrinsic spin using a ferromagnetic gyroscope

An experimental test at the intersection of quantum physics and general relativity is proposed: measurement of relativistic frame dragging and geodetic precession using intrinsic spin of electrons. Furthermore, the behavior of intrinsic spin in spacetime dragged and warped by a massive rotating body is an experimentally open question, hence the results of such a measurement could have important theoretical consequences. Such a measurement is possible by using mm-scale ferromagnetic gyroscopes in orbit around the Earth. Under conditions where the rotational angular momentum of a ferromagnet is sufficiently small, a ferromagnet’s angular momentum is dominated by atomic electron spins and is predicted to exhibit macroscopic gyroscopic behavior. If such a ferromagnetic gyroscope is sufficiently isolated from the environment, rapid averaging of quantum uncertainty via the spin-lattice interaction enables readout of the ferromagnetic gyroscope dynamics with sufficient sensitivity to measure both the Lense-Thirring (frame dragging) and de Sitter (geodetic precession) effects due to the Earth.

79 ASTRONOMY AND ASTROPHYSICS↗

NASA NTRS1967

Determination of the earth's shape

Geometric, classical geodetic, astrogeodetic, gravimetric, and dynamic satellite geodetic methods of determining earth shape

GEOMETRY↗

NASA NTRS1971

Automatic plate mensuration and reduction at Aeronautical Chart and Information Center

The use of optical satellite observation data for geodetic purposes depends on the ability to extract pertinent information from photographic plates by identifying points on the plates and correlating them with known star positions for use in geodetic positioning. This procedure is accomplished with a new semi-automatic measuring system, an advanced analytical plate reduction program for the IBM 7094 computer, and a triangulation adjustment. The advantages gained with the measuring system, a brief discussion of the system itself, and the plate reduction and triangulation adjustment are described.

Seppelin, T. O.↗

NASA NTRS1971

Mission definition study for Stanford relativity satellite. Volume 1: Systems and program

The objective of the relativity satellite mission is to perform an experiment in which a gyroscope in motion about the earth undergoes precession, presumably relativistic, with respect to the fixed stars. Performance of this experiment would clearly test the general theory of relativity and its various modifications. This is the only experiment suggested to date which would confirm the existence of motional drift as well. A mission is defined in which the measurement of the geodetic effect term to 0.2 arc sec/yr is achievable and the measurement of both geodetic and motional drift terms to an accuracy of 0.001 arc sec/yr may be possible. The design of the flying dewar satellite needed to maintain the experiment at cryogenic temperatures is discussed. The gyroscopes, magnetometer, and optical contacting method for dimensional stability of the experimental assembly are considered.

Source record↗

NASA NTRS1972

ALLMAG, GDALMG, LINTRA: Computer programs for geomagnetic field and field-line calculations

A set of computer programs has been developed for the calculation of the geomagnetic field and the tracing of field lines in space. The basic subroutine, geocentric ALLMAG, contains coefficients for seven recently-published field models as built-in data statements. At execution time the user can vary the model and/or the time period by simply changing input parameters. Subroutine GDALMG is adapted for input and output in geodetic coordinates. ALLMAG and GDALMG are equivalent to Cain's FIELD and FIELDG, with the added flexibility of the choice of seven models. LINTRA traces field lines from any point in space to a specified altitude intersect in the same or opposite hemisphere, using any of the models contained in ALLMAG. Input is in either geocentric or geodetic coordinates, and output is returned in both. McIlwain's INVAR package, which calculates B and L, has been adapted to use ALLMAG. All programs are described in detail, and sample calculations are given.

Stassinopoulos, E. G.↗

NASA NTRS1973

Results of Mariner Mars tracking calibration experiment

Ground station network S-band tracking in three-way Doppler modes of Mariner 9 in deep space provided geodetic parameters with an accuracy of 15 meters for use in Apollo 16 and Apollo 17 programs. It was concluded that unified S-band Doppler data provide geodetic results with accuracies comparable to laser ranging data.

Ryan, J. W.↗

NASA NTRS1974

Geometrical geodesy techniques in Goddard earth models

The method for combining geometrical data with satellite dynamical and gravimetry data for the solution of geopotential and station location parameters is discussed. Geometrical tracking data (simultaneous events) from the global network of BC-4 stations are currently being processed in a solution that will greatly enhance of geodetic world system of stations. Previously the stations in Goddard earth models have been derived only from dynamical tracking data. A linear regression model is formulated from combining the data, based upon the statistical technique of weighted least squares. Reduced normal equations, independent of satellite and instrumental parameters, are derived for the solution of the geodetic parameters. Exterior standards for the evaluation of the solution and for the scale of the earth's figure are discussed.

Lerch, F. J.↗

NASA NTRS1974

C-band station coordinate determination for the GEOS-C altimeter calibration area

Dynamical orbital techniques were employed to estimate the center-of-mass station coordinates of six C-band radars located in the designated primary GEOS-C radar altimeter calibration area. This work was performed in support of the planned GEOS-C mission (December, 1974 launch). The sites included Bermuda, Grand Turk, Antigua, Wallops Island (Virginia), and Merritt Island (Florida). Two sites were estimated independently at Wallops Island yielding better than 40 cm relative height recovery, with better than 10 cm and 1 m (relative) recovery for phi and gamma respectively. Error analysis and comparisons with other investigators indicate that better than 2 m relative recovery was achieved at all sites. The data used were exclusively that from the estimated sites and included 18 orbital arcs which were less than two orbital revolutions in length, having successive tracks over the area. The techniques employed here, given their independence of global tracking support, can be effectively employed to improve various geodetic datums by providing very long and accurate baselines. The C-band data taken on GEOS-C should be employed to improve such geodetic datums as the European-1950 using similar techniques.

Krabill, W. B.↗

NASA NTRS1974

Adjustment technique without explicit formation of normal equations /conjugate gradient method/

For a simultaneous adjustment of a large geodetic triangulation system, a semiiterative technique is modified and used successfully. In this semiiterative technique, known as the conjugate gradient (CG) method, original observation equations are used, and thus the explicit formation of normal equations is avoided, 'huge' computer storage space being saved in the case of triangulation systems. This method is suitable even for very poorly conditioned systems where solution is obtained only after more iterations. A detailed study of the CG method for its application to large geodetic triangulation systems was done that also considered constraint equations with observation equations. It was programmed and tested on systems as small as two unknowns and three equations up to those as large as 804 unknowns and 1397 equations. When real data (573 unknowns, 965 equations) from a 1858-km-long triangulation system were used, a solution vector accurate to four decimal places was obtained in 2.96 min after 1171 iterations (i.e., 2.0 times the number of unknowns).

Saxena, N. K.↗

NASA NTRS1972

Delay time measurements of the propagation of radio waves in the atmosphere

The characteristics and operation of the Geodetic Secor System are described. The precision of the ionospheric radiation measurements was determined by a collocation experiment. The EGRS-13 satellite, which was used in the experiment, is discussed. The geodetic network is shown in a diagram form. Conclusions resulting from the experiments are reported.

Rohde, F.↗

NASA NTRS1972

GEODYN system support program, volume 4

The GEODYN Orbit Determination and Geodetic Parameter Estimation System consists of a set of computer programs designed to determine and analyze definitive satellite orbits and their associated geodetic and measurement parameters. This manual describes the Support Programs used by the GEODYN System. The mathematics and programming descriptions are detailed. The operational procedures of each program are presented. GEODYN ancillary analysis programs may be grouped into three different categories: (1) orbit comparison - DELTA (2) data analysis using reference orbits - GEORGE, and (3) pass geometry computations - GROUNDTRACK. All of the above three programs use one or more tapes written by the GEODYN program in either a data reduction or orbit generator run.

Mullins, N. E.↗

NASA NTRS1974

Requirements and applications of marine geodesy and satellite technology to operations in the oceans

Marine geodesy is concerned with the determination of marine geographic positions, geodetic controls, and the geoid. The activities of marine geodesy are related to the utilization of satellite technology, electronic distance measurement, geodetic astronomy, gravimetric geodesy, and the potentially usable very long baseline interferometry. Assessments are made of the different accuracy and/or precision requirements involved in the various approaches. It is shown that marine geodesy is highly relevant to man's various practical and scientific operations at sea, including those on the continental shelves.

Mourad, A. G.↗

NASA NTRS1976

On estimating gravity anomalies: A comparison of least squares collocation with least squares techniques

The least squares collocation algorithm for estimating gravity anomalies from geodetic data is shown to be an application of the well known regression equations which provide the mean and covariance of a random vector (gravity anomalies) given a realization of a correlated random vector (geodetic data). It is also shown that the collocation solution for gravity anomalies is equivalent to the conventional least-squares-Stokes' function solution when the conventional solution utilizes properly weighted zero a priori estimates. The mathematical and physical assumptions underlying the least squares collocation estimator are described, and its numerical properties are compared with the numerical properties of the conventional least squares estimator.

Argentiero, P.↗

NASA NTRS1976

New vertical geodesy

The paper contains a review of the theoretical difference between orthometric heights and heights labeled geometric which are determined through use of an extraterrestrial frame of reference. The theory is supplemented with examples which portray very long baseline interferometry as a measuring system that will provide estimates of vertical crustal motion which are radically improved in comparison with those obtained from analysis of repeated geodetic levelings. The example of the San Fernando earthquake of 1971 is used to show how much estimates of orthometric and geometric height change might differ. A comment by another author is appended which takes issue with some of the conclusions of this paper. In particular, an attempt is made in the comment to rebut the conclusion that geodetic leveling is less reliable than VLBI measurements for determining relative elevation change of points separated by more than 56 km.

Whitcomb, J. H.↗

NASA NTRS1977

On estimating gravity anomalies - A comparison of least squares collocation with conventional least squares techniques

Argentiero, P.↗

NASA NTRS1977

To perform a gyro test of general relativity in a satellite and develop associated control technology

A satellite configuration having two gyroscopes with axes parallel to the boresight of a telescope and two at right angles to the telescope and approximately parallel and perpendicular to the earth's axis is proposed for measuring geodetic precessions due to the earth's motion about the sun, higher order geodetic terms calculated from the earth's quadrapole mass moment (0.010 arc-sec/year in a 400 nautical mile polar orbit), and deflection by the sun of the starlight signal for the reference telescope. Data from the experiment also contain large periodic signals due to the annual and orbital aberrations of starlight which are useful in providing a built in reference signal of known amplitude for scaling the relativity signals, and should yield a singularly precise measurement of the parallax of the reference star. The development of the gyroscope and its readout system are discussed, as well as signal integration, drag-free control, and attitude control.

Fairbank, W. M.↗

NASA NTRS1977

NASA Goddard Space Flight Center

The contribution of the Goddard Space Flight Center to the National Geodetic Satellite Program is reported. All of the major types of tracking systems, including those employing optical, electronic, range-and-range-rate, and laser technologies, which were developed and operated by Goddard, are described. The MINITRACK data were used to derive geodetic results. The methods used for the analysis of these data are presented.

Berbert, J. H.↗

NASA NTRS1978

VLBI-laser intercomparison project

The VLBI-laser intercomparison system for assessing geodetic measurements is described. The primary objective of the DSN VLBI-laser intercomparison project is the accurate measurement of baseline vectors, both length and direction, between established geodetic benchmarks. A second objective is the intercomparison between both satellite and lunar laser ranging techniques with VLBI.

Mulhall, B. D. L.↗