SEARCH · Engineering Papers
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Covers observations and nuclear splitting of comet 73P/Schwassmann-Wachmann 3. Gives evidence in the data which argues against models of strengthless cometary nucleus.
Surface water ice on a comet nucleus is the major source of coma gas. Dust, entrained by coma gas, fragments and vaporizes, forming a second, distributed source of coma gas constituents. Ice species more volatile than water ice below the surface of the nucleus are a third source of coma gas. Vapors from these ices, produced by heat penetrating into the nucleus, diffuse through pores outward into the coma. The second and third sources provide minor, but sometimes easily detectible, gaseous species in the coma. We present mixing ratios of observed minor coma constituents relative to water vapor as a function of heliocentric and cometocentric distances and compare these ratios with model predictions, assuming the sources of the minor species are either coma dust or volatile ices in the nucleus.
An attempt to detect Doppler effects on Jupiter during the impact of fragment A of the Shoemaker-Levy 9 comet is discussed. A short description is given of the technique used to observe the impact. Observations are presented, and a theoretical analysis and inter- pretation are given. The instrumentation used is an advanced and more sensitive version of the Magneto-Optical Filter & a 40 cm telescope.
The impacts of fragments K and R of comet Shoemaker-Levy 9 are examined with the aim to interpret the timing of the observed precursors to the main thermal emission event and to correlate the results of ground-based infrared observations with a variety of observations made onboard the Galileo spacecraft. Independent observations of the impact phenomena (of K & R) are combined.
The results of observations of Jupiter's synchrotron radiation during the period surrounding the impacts of comet SL-9 are reported. The observations were made at the Naval Research Laboratory's Maryland Point Observatory 85 foot radio antenna operating at 1665 MHz (18 cm). The data indicate that an increase in the intensity of the synchrotron emission of 23% took place over the full duration of the impact period. The increase was accompanied by two characteristic changes in the beaming curve: a flattening and the creation of brightness temperature variations on hourly timescales. We interpret the latter as longitudinal variations in the beaming curve which suggests a localized mechanism resulting in a redistribution of the radiating electronis in the Jovian radiation belts.
Changes to Jupiter's synchrotron radiation following the impact of Comet Shoemaker-Levy/9 are reported. Also, the consequences are reported for three possible mechanisms that might have caused those changes.
Understanding of comets has made a quantum advance since 1980 due to the Earth-orbiting observatories, to fly-bys of Halley and Giacobini-Zinner, to better ground-based instruments, and to the Shoemaker-Levy 9 impact with Jupiter. The present understanding and future plans are outlined.
The impact comet SL-9 with Jupiter induced a number of variations in Jupiter's synchrotron radiation, including an increase in emission intensity, spectral changes, and a possible broadening in the latitudinal distribution of the emission. Considered are three potential mechanisms for inducing such effects (electron acceleration, radial diffusion, and pitch-angle scattering), and their consequences.
The Galileo Near Infrared Mapping Spectrometer (NIMS) observed the impacts of the C, F, G, and R fragments of Comet Shoemaker-Levy 9 on Jupiter in July 1994.
Results from the encounters with comets Giocobini-Zinner, Halley, and Grigg-Skjellerup are reviewed.
This paper describes two aspects to the comet and asteroid hazard problem.
The strong propensity of the SOHO sungrazing comets for clustering is a product of their runaway fragmentation throughout the orbit about the Sun.
X-ray emission from a comet was observed for the first time in 1996. One of the mechanisms believed to be contributing to this surprisingly strong emission is the interaction of highly charged solar wind ions with cometary gases.
We report extensive observations of striation patterns in the dust tail of comet Hale-Bopp (C/1995 O1) over a period of more than 10 weeks, from mid-february until early May 1997.
Jupiter will be bombarded by the debris of P/Shoemaker-Levy 9 that populated the comet's west-southwestern trail.
The motions of all known Earth approaching asteroids and comets with reasonably secure orbits have been numerically integrated forward in time to A.D. 2200. Special care was taken to use the best available initial conditions including orbits based upon radar data.
Deep Impact is NASA's eighth Discovery mission. This low-cost, focused planetary science investigation gathered the data necessary to help scientists unlock early secrets of our solar system. The comet encounter with Tempel 1 was a complex event - requiring extremely accurate timing, robustness to an unknown environment, and flight team adaptibility. The mission operations and flight systems performance were spectacular for approach, impact, and lookback imaging on July 4, 2005.
Deep Impact is NASA's eighth Discovery mission. This low-cost, focused planetary science investigation gathered the data necessary to help scientists unlock early secrets of our solar system. The comet encounter with Tempel 1 was a complex event - requiring extremely accurate timing, robutstness to an unknown environment, and flight team adaptability. The mission operations and flight systems performance were spectacular for approach, impact, and lookback imaging on July 4, 2005.