The Experts below are selected from a list of 4116 Experts worldwide ranked by ideXlab platform
R A Jacobson - One of the best experts on this subject based on the ideXlab platform.
-
the orbits of the uranian satellites and rings the gravity field of the uranian system and the orientation of the pole of uranus
The Astronomical Journal, 2014Co-Authors: R A JacobsonAbstract:French et al. determined the orbits of the Uranian rings, the orientation of the pole of Uranus, and the gravity harmonics of Uranus from Earth-based and Voyager ring occultations. Jacobson et al. determined the orbits of the Uranian satellites and the masses of Uranus and its satellites from Earth-based astrometry and observations acquired with the Voyager 2 Spacecraft; they used the gravity harmonics and pole from French et al. Jacobson & Rush reconstructed the Voyager 2 trajectory and redetermined the Uranian system gravity parameters, satellite orbits, and ring orbits in a combined analysis of the data used previously augmented with additional Earth-based astrometry. Here we report on an extension of that work that incorporates additional astrometry and ring occultations together with improved data processing techniques.
-
the orbits of the inner uranian satellites from hubble space telescope and Voyager 2 observations
The Astronomical Journal, 1998Co-Authors: R A JacobsonAbstract:This article presents revised orbital elements for the 10 small Uranian satellites discovered by the Voyager 2 Spacecraft. The elements have been determined from a fit to astrometric observations made with the Hubble Space Telescope and imaging data acquired by Voyager 2. An assessment of the accuracy of the orbits represented by the elements is provided, as are comparisons with orbits found by previous investigators.
-
the orbit of phoebe from earthbased and Voyager observations
Astronomy & Astrophysics Supplement Series, 1998Co-Authors: R A JacobsonAbstract:This article presents the results of a fit of a numerically integrated orbit for the Saturnian satellite Phoebe to Earthbased astrometric observations (from 1904 to 1996) and imaging data acquired by the Voyager 2 Spacecraft during its encounter with Saturn. The primary results are the epoch state vector for the integration and a set of mean orbital elements which approximately represent the orbit. An assessment of the quality of the fit and the accuracy of the orbit is also provided.
-
astrographic observations of the major uranian satellites from Voyager 2
Astronomy & Astrophysics Supplement Series, 1992Co-Authors: R A JacobsonAbstract:This article provides the reduced astrographic observations of the major Uranian satellites derived from star-satellite imaging data acquired by the Voyager 2 Spacecraft. The data set contains 445 sets of Spacecraft-centered right ascension and declination observations and includes all of the observations used in Voyager encounter operations. The conversion process from imaging to astrographic observations was identical to that used for the Neptunian satellites (Jacobson 1991). The effect of using the astrographic rather than imaging form in ephemeris improvement is evaluated.
-
the masses of uranus and its major satellites from Voyager tracking data and earth based uranian satellite data
The Astronomical Journal, 1992Co-Authors: R A Jacobson, J K Campbell, A H Taylor, S P SynnottAbstract:Improved values for the masses of the Uranian system and the satellites Ariel, Umbriel, Titania, Oberon, and Miranda are obtained on the basis of an analysis of the Doppler-tracking data and star-satellite imaging from the Voyager 2 Spacecraft combined with earth-based astrometric satellite observations. Masses are expressed as the product, the universal gravitational constant times the mass of the body, in units of (cu km/sq s). The satellite masses are (4.4 +/- 0.5) for Miranda, (90.3 +/- 8.0) for Ariel, (78.2 +/- 9.0) for Umbriel, (235.3 +/- 6.0) for Titania, and (201.1 +/- 5.0) for Oberon. Quoted errors are standard errors and are the present assessment of the true rather than the formal errors. The Uranus rotational pole orientation angles and gravity harmonic coefficients were fixed at the values determined by French et al. (1988) from stellar occultations of the Uranian rings observed from both the earth and Voyager 2 and from the occultation of the Spacecraft radio signal.
Colin J. Joyce - One of the best experts on this subject based on the ideXlab platform.
-
observation of bernstein waves excited by newborn interstellar pickup ions in the solar wind
The Astrophysical Journal, 2012Co-Authors: Colin J. Joyce, Charles W. Smith, Philip A. Isenberg, Neil Murphy, Peter S Gary, Perry Gray, L F BurlagaAbstract:A recent examination of 1.9 s magnetic field data recorded by the Voyager 2 Spacecraft in transit to Jupiter revealed several instances of strongly aliased spectra suggestive of unresolved high-frequency magnetic fluctuations at 4.4 AU. A closer examination of these intervals using the highest resolution data available revealed one clear instance of wave activity at Spacecraft frame frequencies from 0.2 to 1 Hz. Using various analysis techniques, we have characterized these fluctuations as Bernstein mode waves excited by newborn interstellar pickup ions. We can find no other interpretation or source consistent with the observations, but this interpretation is not without questions. In this paper, we report a detailed analysis of the waves, including their frequency and polarization, that supports our interpretation.
-
excitation of low frequency waves in the solar wind by newborn interstellar pickup ions h and he as seen by Voyager at 4 5 au
The Astrophysical Journal, 2010Co-Authors: Colin J. Joyce, Charles W. Smith, Philip A. Isenberg, Neil Murphy, N A SchwadronAbstract:We report the observation of a spectral enhancement in the magnetic field fluctuations measured by the MAG instrument on the Voyager 2 Spacecraft during 4.5 hr on DOY 7, 1979 at a heliocentric radial position of 4.5?AU. This time period is contained within a solar wind rarefaction when the large-scale interplanetary magnetic field was nearly radial. The frequency range and polarization of the enhanced fluctuations are consistent with waves generated by newly ionized interstellar H+ and He+. We show sunward propagation of the waves via a cross-helicity analysis. We compare the observation with a theoretical model and find reasonable agreement given the model assumptions. This event is the first indication of pickup ion-generated waves seen at Voyager. It is also the first identification of pickup He+ waves by any Spacecraft.
L F Burlaga - One of the best experts on this subject based on the ideXlab platform.
-
observation of bernstein waves excited by newborn interstellar pickup ions in the solar wind
The Astrophysical Journal, 2012Co-Authors: Colin J. Joyce, Charles W. Smith, Philip A. Isenberg, Neil Murphy, Peter S Gary, Perry Gray, L F BurlagaAbstract:A recent examination of 1.9 s magnetic field data recorded by the Voyager 2 Spacecraft in transit to Jupiter revealed several instances of strongly aliased spectra suggestive of unresolved high-frequency magnetic fluctuations at 4.4 AU. A closer examination of these intervals using the highest resolution data available revealed one clear instance of wave activity at Spacecraft frame frequencies from 0.2 to 1 Hz. Using various analysis techniques, we have characterized these fluctuations as Bernstein mode waves excited by newborn interstellar pickup ions. We can find no other interpretation or source consistent with the observations, but this interpretation is not without questions. In this paper, we report a detailed analysis of the waves, including their frequency and polarization, that supports our interpretation.
Philip A. Isenberg - One of the best experts on this subject based on the ideXlab platform.
-
observation of bernstein waves excited by newborn interstellar pickup ions in the solar wind
The Astrophysical Journal, 2012Co-Authors: Colin J. Joyce, Charles W. Smith, Philip A. Isenberg, Neil Murphy, Peter S Gary, Perry Gray, L F BurlagaAbstract:A recent examination of 1.9 s magnetic field data recorded by the Voyager 2 Spacecraft in transit to Jupiter revealed several instances of strongly aliased spectra suggestive of unresolved high-frequency magnetic fluctuations at 4.4 AU. A closer examination of these intervals using the highest resolution data available revealed one clear instance of wave activity at Spacecraft frame frequencies from 0.2 to 1 Hz. Using various analysis techniques, we have characterized these fluctuations as Bernstein mode waves excited by newborn interstellar pickup ions. We can find no other interpretation or source consistent with the observations, but this interpretation is not without questions. In this paper, we report a detailed analysis of the waves, including their frequency and polarization, that supports our interpretation.
-
excitation of low frequency waves in the solar wind by newborn interstellar pickup ions h and he as seen by Voyager at 4 5 au
The Astrophysical Journal, 2010Co-Authors: Colin J. Joyce, Charles W. Smith, Philip A. Isenberg, Neil Murphy, N A SchwadronAbstract:We report the observation of a spectral enhancement in the magnetic field fluctuations measured by the MAG instrument on the Voyager 2 Spacecraft during 4.5 hr on DOY 7, 1979 at a heliocentric radial position of 4.5?AU. This time period is contained within a solar wind rarefaction when the large-scale interplanetary magnetic field was nearly radial. The frequency range and polarization of the enhanced fluctuations are consistent with waves generated by newly ionized interstellar H+ and He+. We show sunward propagation of the waves via a cross-helicity analysis. We compare the observation with a theoretical model and find reasonable agreement given the model assumptions. This event is the first indication of pickup ion-generated waves seen at Voyager. It is also the first identification of pickup He+ waves by any Spacecraft.
Neil Murphy - One of the best experts on this subject based on the ideXlab platform.
-
observation of bernstein waves excited by newborn interstellar pickup ions in the solar wind
The Astrophysical Journal, 2012Co-Authors: Colin J. Joyce, Charles W. Smith, Philip A. Isenberg, Neil Murphy, Peter S Gary, Perry Gray, L F BurlagaAbstract:A recent examination of 1.9 s magnetic field data recorded by the Voyager 2 Spacecraft in transit to Jupiter revealed several instances of strongly aliased spectra suggestive of unresolved high-frequency magnetic fluctuations at 4.4 AU. A closer examination of these intervals using the highest resolution data available revealed one clear instance of wave activity at Spacecraft frame frequencies from 0.2 to 1 Hz. Using various analysis techniques, we have characterized these fluctuations as Bernstein mode waves excited by newborn interstellar pickup ions. We can find no other interpretation or source consistent with the observations, but this interpretation is not without questions. In this paper, we report a detailed analysis of the waves, including their frequency and polarization, that supports our interpretation.
-
excitation of low frequency waves in the solar wind by newborn interstellar pickup ions h and he as seen by Voyager at 4 5 au
The Astrophysical Journal, 2010Co-Authors: Colin J. Joyce, Charles W. Smith, Philip A. Isenberg, Neil Murphy, N A SchwadronAbstract:We report the observation of a spectral enhancement in the magnetic field fluctuations measured by the MAG instrument on the Voyager 2 Spacecraft during 4.5 hr on DOY 7, 1979 at a heliocentric radial position of 4.5?AU. This time period is contained within a solar wind rarefaction when the large-scale interplanetary magnetic field was nearly radial. The frequency range and polarization of the enhanced fluctuations are consistent with waves generated by newly ionized interstellar H+ and He+. We show sunward propagation of the waves via a cross-helicity analysis. We compare the observation with a theoretical model and find reasonable agreement given the model assumptions. This event is the first indication of pickup ion-generated waves seen at Voyager. It is also the first identification of pickup He+ waves by any Spacecraft.
