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Results for “comets Shoemaker-Levy”

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.

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At least 91 records · Page 5
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NASA NTRS1994

Comet Impact Tape 4

Continued press coverage of the comet Shoemaker-Levy 9 impact on the surface of Jupiter is presented. This tape covers 18 Jul. 1994.

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NASA NTRS1994

Comet Impact Tape 5

Continued press coverage of the comet Shoemaker-Levy 9 impact on the surface of Jupiter is presented. This tape covers 19 Jul. 1994.

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NASA NTRS1994

Comet Impact Tape 6

Continued press coverage of the comet Shoemaker-Levy 9 impact on the surface of Jupiter is presented. This tape covers 20 Jul. 1994.

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NASA NTRS1994

Comet Impact Tape 7

Continued press coverage of the comet Shoemaker-Levy 9 impact on the surface of Jupiter is presented. This tape covers 21 Jul. 1994.

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NASA NTRS1994

Comet Impact Tape 8

Continued press coverage of the comet Shoemaker-Levy 9 impact on the surface of Jupiter is presented. This tape covers 22 Jul. 1994.

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NASA NTRS1994

Comet Impact Tape 9

Continued press coverage of the comet Shoemaker-Levy 9 impact on the surface of Jupiter is presented. This tape covers 23 Jul. 1994.

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NASA NTRS1994

Comet Impact Tape 3

Continued press coverage of the comet Shoemaker-Levy 9 impact on the surface of Jupiter is presented. This tape covers 17 Jul. 1994.

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NASA NTRS1994

Global oscillation amplitudes excited by the Jupiter-comet collision

The energy released during the collision of fragments of comet Shoemaker-Levy 9 with Jupiter in 1994 July may excite a spectrum of global oscillation modes. We estimate the maximum amplitudes to which the p-modes, discontinuity modes, inertial modes, and r-modes can be excited by assuming that the full kinetic energy of the fragment, which we take to be 10(exp 30) ergs, is converted into the energy of each individual mode. We have used two realistics Jovian models as the basis for our estimates: one with and one without the predicted 'plasma phase transition' (PPT) of hydrogen. A density discontinuity in the planet's hydrogen-helium envelope is associated with the PPT. We find that high-frequency p-modes, with periods approximately less than 15 minutes, may be excited to sufficiently large amplitudes to be observable as Doppler shifts (velocity amplitudes approximately greater than serveral m/s) or temperature variations (delta(T) approximately greater than 0.01 K) at the planetary surface. Inertial modes may also be observable. If the PPT exists in Jupiter, inertial modes with periods approximately 8 hr or approximately 2.2 days trapped in the surface region of the planet, above the PPT, may be detectable as temperature fluctuations of order delta(T) approximately 0.01 K. Inertial modes with periods of order 8-8.5 hr appear to be particularly strongly excited if the PPT exists. If the PPT does not exist in Jupiter, intertial modes with periods approximately 8-8.5 hr have much lower amplitudes. In this case, inertial modes with periods longer than approximately 18 hr may produce temperature fluctuations of order delta(T) approximately 0.01 K. Discontinuity modes associated with the PPT and r-modes unfortunately may not reach observable amplitudes.

Lee, U.↗
NASA NTRS1994

New jovian ring?

We follow the orbital evolution of small dust particles generated from the break up of comet Shoemaker-Levy 9 (SL9). In addition to the usual perturbations, we also consider electrostatic charging and the consequent magnetospheric effects. We show, that in about ten years following the break up, a small fraction of the dust will settle into orbits well inside the magnetosphere. The forming ring will be comprised of dust particles with radii in the range of 1.5 less than alpha less than 2.5 micrometers that follow retrograde orbits in the radial range of 4.5 less than r less than 6 R(sub J). We estimate the peak optical depth of this new ring in the range of 10(exp -8) less than tau(sub max) less than 2 x 10(exp -6).

Horanyi, Mihaly↗
NASA NTRS1994

Impacts with the Earth and Jupiter

The Earth has been subject to impacts from comets and asteroids since its formation, and such impacts have played an important role in the evolution of life on our planet. We now recognize not only the historical role of impacts, but the contemporary hazard posed by such events. In the absence of a complete census of potentially threatening Earth-crossing asteroids or comets (called collectively Near Earth Objects, or NEOs), or even of a comprehensive current search program to identify NEOs, we can consider the hazard only from a probabilistic perspective. In general, the larger the object the greater the hazard, even when allowance is made for the infrequency of large impacts. Most of the danger to human life is associated with impacts by objects roughly 2 km or larger (energy greater than 1 million megatons), which can inject sufficient submicrometer dust into the atmosphere to produce a severe short-term global cooling with subsequent loss of crops, leading to starvation. Hazard estimates suggest that the chance of such an event occurring during a human lifetime is about 1:5000, and the global probability of death from such impacts is of the order of 1:20000, values that can be compared with risks associated with other natural hazards such as earthquakes, volcanic eruptions, and severe storms. The widely-observed impact of Comet Shoemaker-Levy 9 with Jupiter in July 1994 provides a graphic example of such an interplanetary collision and is stimulating worldwide interest in protecting our planet against cosmic impact catastrophes.

Morrison, David↗
NASA NTRS1994

The Big Fizzle

How will the fragments of comet Shoemaker-Levy 9 meet their end, with a bang or a whimper?.

Shoemaker-Levy 9 cometary nuclei primordial solar ↗
NASA NTRS1995

Doppler Observations of the Impact of Comet SL9 Fragment A

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.

Shoemaker-Levy 9 Jupiter comet fragment A doppler ↗
NASA NTRS1995

Kuiper Airborne Observatory's Telescope Stabilization System: Disturbance Sensitivity Reduction Via Velocity Loop Feedback

In July of 1994 the Kuiper Airborne Observatory's (KAO) Telescope Stabilization System (TSS) was upgraded to meet performance goals necessary to view the Shoemaker-Levy 9 comet collision with Jupiter. The KAO is a modified C-141 Aircraft supporting a 36 inch Infrared telescope used to gather and analyze astronomical data. Before the upgrade, the TSS exhibited approximately a 10 arc-second resolution pointing accuracy. The majority of the inaccuracy was attributable to aircraft vibration and wind buffeting entering through the aircraft's telescope door opening; in other words, the TSS was overly sensitive to external disturbances. Because of power limitations and noise requirements, improving the pointing accuracy of the telescope required more sophistication than simply raising the bandwidth as some classical control strategies might suggest. Instead, relationships were developed between the disturbance sensitivity and closed loop transfer functions. These relationships suggested that employing velocity feedback along with an increase in current loop gain would dramatically improve the pointing resolution of the TSS by decreasing the control system's sensitivity to external disturbances. With the implementation of some classical control techniques and the above philosophy, the KAO's TSS's resolution was improved to approximately 2-3 arc-seconds.

Lawrence, David P.↗
NASA NTRS1995

Comets: What Do We Know and Where Do We Go From Here?

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.

comets Shoemaker-Levy↗