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Anderson, John D.

Publications and source records attributed to Anderson, John D..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2005

Measurement of the PPN Parameter (gamma) with radio signals from the Cassini Spacecraft at X- and Ka-Bands

Radio Doppler data from the Cassini spacecraft during its solar conjunction in June 2002 can be used to measure the bending of light by solar gravitation. In terms of the standard post-Newtonian parameter (gamma), we find that (gamma) - 1 = (-1.3 +/- 5.2)x10^-5 in agreement with the theory of General Relativity. This result implies that the parameter (omega) in the Brans-Dicke theory is greater than 9000 at a 95% confidence level.

radio science↗
NASA NTRS2005

Amalthea's density is less than that of water

Radio Doppler data from the Galileo spacecraft's encounter with Amalthea, one of Jupiter's small inner moons, on 5 November 2002 yield a mass of (2.08 +/- 0.15) x 10(18) kilograms. Images of Amalthea from two Voyager spacecraft in 1979 and Galileo imaging between November 1996 and June 1997 yield a volume of (2.43 +/- 0.22) x 10(6) cubic kilometers. The satellite thus has a density of 857 +/- 99 kilograms per cubic meter. We suggest that Amalthea is porous and composed of water ice, as well as rocky material, and thus formed in a cold region of the solar system, possibly not at its present location near Jupiter.

Jupiter↗
NASA NTRS2004

Laser ranging to the Moon, Mars and beyond

This paper discusses the current state and the future improvements in the tests of relativistic gravity with Lunar Laser Ranging (LLR). We also consider precision gravitational tests with the future laser ranging to Mars and discuss optical design of the proposed Laser Astrometric Test of Relativity (LATOR) mission. We emphasize that already existing capabilities can offer significant improvements not only in the tests of fundamental physics, but may also establish the infrastructure for space exploration in the near future. Looking to future exploration, what characteristics are desired for the next generation of ranging devices, what is the optimal architecture that would benefit both space exploration and fundamental physics, and what fundamental questions can be investigated? We try to answer these questions.

Murphy, Thomas W. Jr.↗
NASA NTRS1999

The Interactions of a Flame and Its Self-Induced Boundary Layer

The interaction of a laminar flame with its self-generated boundary layer in a rectangular channel was numerically simulated using the two-dimensional, reacting, Navier-Stokes equations. A two species chemistry model was implemented which simulates the stoichiometric reaction of acetylene and air. Calculations were performed to investigate the effects of altering the boundary condition of the wall temperature, the Lewis number, the dynamic viscosity, and the ignition method. The purpose of this study was to examine the fundamental physics of the formation of the boundary layer and the interaction of the flame as it propagates into the boundary layer that its own motion has created.

Ott, James D.↗
NASA NTRS1997

Spacecraft Tests of General Relativity

Current spacecraft tests of general relativity depend on coherent radio tracking referred to atomic frequency standards at the ground stations. This paper addresses the possibility of improved tests using essentially the current system, but with the added possibility of a space-borne atomic clock. Outside of the obvious measurement of the gravitational frequency shift of the spacecraft clock, a successor to the suborbital flight of a Scout D rocket in 1976 (GP-A Project), other metric tests would benefit most directly by a possible improved sensitivity for the reduced coherent data. For purposes of illustration, two possible missions are discussed. The first is a highly eccentric Earth orbiter, and the second a solar-conjunction experiment to measure the Shapiro time delay using coherent Doppler data instead of the conventional ranging modulation.

Anderson, John D.↗
NASA NTRS1996

Spacecraft Tests of General Relativity

This paper addresses the possibility of improved tests using essentially the current systems, but with the added possibility of a space-borne atomic clock.

Relativity↗
NASA NTRS1995

Improved Bounds on Nonluminous Matter in Solar Orbit

We improve, using a larger set of observations including Voyager 2 Neptune flyby data, previous bounds on the amount of dark matter (DM) trapped in a spherically symmetric distribution about the Sun. We bound DM by noting that such a distribution would increase the effective mass of the Sun as seen by the outer planets and by finding the uncertainty in that effective mass for Uranus and Neptune in fits to the JPL developmental ephemeris residuals, including optical data and those two planets' Voyager 2 flybys. We extend our previous procedure by fitting more parameters of the developmental ephamerides. In addition, we present here the values for Pioneer 10, Pioneer 11, Voyager 1, and Voyager 2 Jupiter-ranging normal points (and incorporate these data as well). Our principal result is to limit DM in spherically symmetric distributions in orbit about the Sun interior to Neptune's orbit to less than Earth mass and interior to Uranus's orbit to about 1/6 of Earth's mass.

Anderson, John D.↗
NASA NTRS1993

Voyager 2 Test Of The Radar Time-Delay Effect

Report presents analysis of radio range measurements generated during superior solar conjunction of Voyager 2 spacecraft in December 1985. One in continuing series of studies directed toward verifying prediction, according to theory of general relativity, that electromagnetic signal propagating near Sun is delayed by solar gravitational field.

Krisher, Timothy P.↗
NASA NTRS1993

The Galileo solar redshift experiment

From the October 1989 launch to the first December 1990 earth gravity assist, we regularly obtained frequency measurements of the spacecraft clock - an ultrastable crystal oscillator (USO) supplied by Frequency Electronics, Inc. The solar gravitational redshift in frequency was readily detectable, and because of the unique variations in heliocentric distance we could separate the general relativistic effects from the USO's intrinsic frequency variations. We have verified the total frequency shift predicted by general relativity to 0.5 percent accuracy, and the solar gravitational redshift to 1 percent accuracy.

Krisher, Timothy P.↗
NASA NTRS1992

Retrieval of a wind profile from the Galileo Probe telemetry signal

The zonal wind speed profile within Jupiter's upper troposphere is to be estimated on the basis of its influence on the frequency of the Galileo Probe's telemetry signal; this is achieved by linearizing the relativistic Doppler shift equation about a state of zero wind speed, expanding the zonal wind series in a Legendre polynomial series, and reducing the resulting equations to a linear, least-squares problem. If the error sources have magnitudes not greater than those presently assumed, the retrieved wind speed profiles can place a key constraint on the basic drive for the atmospheric circulation, as well as anchoring winds derived from Galileo Orbiter images to well-defined vertical positions in the atmosphere.

Pollack, James B.↗
NASA NTRS1991

Voyager 2 test of the radar time-delay effect

By analyzing radio range measurements generated during the solar conjunction of the Voyager 2 spacecraft in 1985, the relativistic time-delay effect has been tested accurately with a spacecraft at a distance of 3 x 10 to the 9th km from the earth. Because the range measurements were generated simultaneously at two frequencies on the downlink, it was possible to derive calibrations for the delay resulting from intervening solar plasma. In addition, a record of attitude thruster firings was used to model small accelerations of the spacecraft that could have produced a range error. It was thereby possible to determine the parameterized post-Newtonian parameter gamma to an accuracy of 3 percent with only a sparse amount of range data.

Krisher, Timothy P.↗
NASA NTRS1991

Physical properties of the Uranian satellites

Data regarding the Uranian satellites' radii, masses, mean density, and, consequently, their internal structures obtained from the Voyager encounter are analyzed. Topics covered are the sizes, shapes, topography, masses, densities, and models of the internal structures of the five major satellites. The sizes and shapes of the 10 small satellites discovered by Voyager 2 are discussed. The physical properties of the large satellites of Uranus are compared to those other satellites in the outer solar system, particularly those of Jupiter and Saturn, and the implications that these comparisons have for understanding the origin and evolution of the satellites of Uranus are discussed.

Brown, Robert H.↗
NASA NTRS1991

Radar and spacecraft ranging to Mercury between 1966 and 1988

Improved solutions have been obtained for the orbit and equatorial cross-section of Mercury using radar ranging data spanning 22 years. These data have yielded new results on the precession of Mercury's perihelion and better limits on a possible time variation in the gravitational constant G.

Anderson, John D.↗
NASA NTRS1991

Small body mass determination from a flyby

This paper investigates the accuracy with which the mass of a small body can be determined from a flyby. Due to the nearly linear nature of hyperbolic flybys of small bodies, analytic solutions can be derived. Four analytic solutions are developed, each of increasing complexity with different applications. These solutions are compared to a complex computer simulation for accuracy. When these methods are applied to nearly linear trajectories, the analytic solutions agree with the computer simulation results to within 4.0 percent except in one boundary case which is discussed in the text. Also described is the linear range for which these equations are applicable. These solutions are then applied to the proposed asteroid flyby of the CRAF mission to predict the mass estimate accuracy.

Sybert, Catherine B.↗
NASA NTRS1990

Test of the gravitational redshift effect at Saturn

The results of a test of the gravitational redshift effect at Saturn are reported. Measurements of the redshift were obtained with the Voyager 1 spacecraft during its encounter with Saturn in 1980. Because the spacecraft was equipped with an ultrastable crystal oscillator (USO), it is possible to test the redshift effect at an interesting level of accuracy. Assuming that radiation in the Saturn magnetosphere has had a negligible effect on the USO, the prediction of general relativity to an accuracy of 1 percent is verified. This limit could be of interest for constraining possible alternative theories of gravity.

Krisher, Timothy P.↗