Engineering topics

Ip, W. H.

Publications and source records attributed to Ip, W. H..

9 records

NASA NTRS1996

(abstract) Microwave Instrument for Rosetta Orbiter (MIRO)

MIRO is a scientific instrument designed for the orbiter of the Rosetta International Mission. It will address the nature of the cometary nucleus, outgassing, and the development of the coma as strongly interrelated aspects of cometary physics. Detailed parameters of the MIRO instrument and the scientific objectives to be met will be discussed. Simulated observations with the MIRO instrument will be shown.

comet microwaves MIRO Microwave Instrument for Ros↗

NASA NTRS1996

Rosetta Radio Science Investigations

The Rosetta Radio Science Investigations (RSI) experiment was selected by the European Space Agency to be included in the International Rosetta Mission to comet P/Wirtanen (launch in 2003, arrival and operational phase at the comet 2011-2013). The RSI science objectives address fundamental aspects of cometary physics such as the mass and bulk density of the nucleus, the gravity field, non-gravitational forces, the size and shape, the internal structure, the composition and roughness of the nucleus surface, the abundance of large dust grains and the plasma content in the coma and the combined dust and gas mass flux on the orbiter. RSI will make use of the radio system of the Rosetta spacecraft.

P/Wirtanen radio science cometary physics cometary↗

NASA NTRS1985

Gradients and anisotropies of high energy cosmic rays in the outer heliosphere

Previous studies at lower energies have shown that the cosmic ray density gradients vary in space and time, and many authors currently are suggesting that the radial gradient associated with solar cycle modulation is supported largely by narrow barriers which encircle the Sun and propagate outward with the solar wind. If so, the anisotropy is a desirable way to detect spatial gradients, because it can be associated with the local solar wind and magnetic field conditions. With this in mind, the anisotropy measurements made by the UCSD Cerenkov detectors on Pioneers 10 and 11 are studied. It is shown that the local anisotropy varies greatly, but that the long term average is consistent with the global radial gradient measured between two spacecraft over a baseline of many AU.

Fillius, W.↗

NASA NTRS1985

Gradients and anisotropies of high energy cosmic rays in the outer heliosphere

Two cosmic rays which pass through the same point going in opposite directions will, in the absence of scattering and inhomogeneities in the magnetic field, trace helices about adjacent flux tubes, whose centerlines are separated by one gyrodiameter. A directional anisotropy at the point suggests a difference in the number of cosmic rays loading the two flux tubes; that is, a density gradient over the baseline of a gyrodiameter. Previous studies at lower energies have shown that the cosmic ray density gradients vary in time and space. It is suggested that the radial gradient associated with solar cycle modulation is supported largely by narrow barriers which encircle the sun and propagate outward with the solar wind. If so, the anisotropy is a desirable way to detect spatial gradients, because it can be associated with the local solar wind and magnetic field conditions. Anisotropic measurements made by Cerenkov detectors on Pioneers 10 and 11 were studied. It was found that local anisotropy varies greatly, but that the long term average is consistent with the global radial gradient measured between two spacecraft over a baseline of many AU.

Fillius, W.↗

NASA NTRS1981

X-ray and energetic neutral particle emission from Saturn's magnetosphere

A description is presented of observations of the Voyager 1 spacecraft obtained a few days before encounter of the Saturn magnetosphere in November 1980. As Voyager 1 has no special experiment onboard for X-ray and neutral particle detection, the sensitivity and directional measurements of the low energy charged particle (LECP) analyzer is used to identify the neutral radiation above the charged particle background. The LECP telescope uses a silicon detector of 96.6 micrometers thickness and 0.08 sq cm area to accumulate counts in eight separate sectors near the ecliptic plane. The existence of radiation above the detector background emanating from the vicinity of Saturn, upstream from the bow shock is shown. The excess counts are most plausibly attributed to neutral radiation, that is, X rays and/or neutral energetic particles. However, in connection with quantitative considerations the observed excess counts are probably not due to X-rays. It is concluded that charge exchange of energetic ions with satellite tori is an important loss mechanism at Saturn as well as at Jupiter.

Kirsch, E.↗

NASA NTRS1981

Atomic clouds as distributed sources for the plasma torus

Implications of recent developments for the neutral particle environment of Jupiter are considered. The first detection is reported of very hot S+ ions with gyrospeeds comparable to the corotations speed, a phenomenon which results from a neutral sulfur cloud. Evidence supports the hypothesis that extensive neutral clouds of oxygen and sulfur exist and are important sources of ions and energy for the Io torus.

Brown, R. A.↗

NASA NTRS1980

Trapped radiation belts of Saturn - First look

Data on the magnetosphere of Saturn obtained with the trapped radiation detector package on board the Pioneer 11 spacecraft is reported. Radiation belt profiles determined by the trapped radiation detectors on Pioneer 10 and 11 indicate that Saturn's magnetosphere is intermediate in size between those of the earth and Jupiter, with particle intensities similar to those of the earth. The outer region of the Saturn magnetosphere is found to contain particles of lower energy than the outer region, being strongly influenced by the time-varying solar wind. The moons and rings of Saturn are observed to be effective absorbers of trapped particles, confirming the discoveries of the F ring, the Pioneer ring division and the moon 1979 S 2. Particle diffusion rates are used to estimate a cross-sectional area of greater than 7 x 10 to the 13th sq cm and an opacity greater than 0.00001 for the F ring. It is suggested that cosmic-ray albedo neutron decay be studied as a possible source of energetic particles in the inner magnetosphere of Saturn.

Fillius, W.↗

NASA NTRS1977

On the early scattering processes of the outer planets

The gradual scattering of small bodies by the Jovian planets in the late stage of their accretion is simulated by Monte Carlo calculation. The effects of collisional interaction of the scattered planetesimals with the inner planets and asteroidal belt are estimated. The total mass influx injected into the terrestrial zones from the outer planetary zone could be appreciable; however, if the damping effects due to the mutual inelastic or catastrophic collisions among the small bodies were significant, the total mass influx would be greatly reduced. The origin of the cometary Oort cloud in relation to these scattering processes is also discussed. The calculation indicates that, in addition to Jupiter, Uranus and Neptune were likely to be the major contributors to the population of long-period comets if they originated from such scattering processes.

Ip, W. H.↗

NASA NTRS1974

Application of the Brown-Shook model to the Kirkwood gaps and resonant asteroids

The mathematical model developed by Brown and Shook is used to explain the absence of asteroids in the Kirkwood gaps as well as the existence of some resonant asteroids with orbital periods commensurable to that of Jupiter. In addition, this model can possibly explain the biased number distributions at the commensurable positions of both resonant gaps and clusters. However, this resonant model is probably not applicable to the Saturnian ring system due to the possible cosmogonic plasma process during its formation.

Ip, W. H.↗