Engineering topics

Hanner, M. S.

Publications and source records attributed to Hanner, M. S..

At least 55 records · Page 3

NASA NTRS1988

Cometary dust composition

The earth based measurements and in situ sampling of Comet Halley have provided new data about the chemical composition of cometary grains. Recent progress in laboratory studies of interplanetary dust particles (IDPs) complement the comet data, allowing inferences about the mineralogy and physical structure of the comet dust to be drawn from the observed elemental composition and infrared spectra. The in situ dust composition measurements at Halley, the composition of IDPs and their relation to comet dust, and the origin of the 3.4 micron hydrocarbon feature is discussed. Related discussion is also presented on aromatic components in comets and the 3.4 micron feature. These topics are briefly summarized.

Gehrz, R. D.↗

NASA NTRS1987

Infrared emission from P/Halley's dust coma during March 1986

Photometry at 2-20 microns of the inner dust coma of comet Halley was obtained at the NASA IRTF on March 6.85, 12.8, 13.75, 17.7, and 24.8. Positions offset 10 arcsec were measured as well as the central brightness. The strength of the 10 micron emission feature was observed to vary with location in the coma. The infrared emission is in general agreement with the dust size distribution measured from the Vega and Giotto spacecraft. March 6.8, 17.7, and 24.8 corresponded to strong dust jet activity. The strength of the 10 micron silicate emission is shown to be a sensitive indicator of grain size and thus of jet activity. Dust production rate on March 13.75, 6 hr before Giotto encounter, was about 10 to the 7th gm/s.

Hanner, M. S.↗

NASA NTRS1987

The dust distribution within the inner coma of comet P/Halley 1982i - Encounter by Giotto's impact detectors

Analyses are presented of Giotto's Dust Impact Detection System experiment measurements of dust grains incident on the Giotto dust shield along its trajectory through the coma of comet P/Halley on March 13 and 14, 1986. Ground-based CCD imagery of the inner coma dust continuum at the time of the encounter are used to derive the area of grains intercepted by Giotto. Data obtained at large masses show clear evidence of a decrease in the mass distribution index at these masses within the coma; it is shown that such a value of the mass index can furnish sufficient mass for consistency with an observed deceleration.

Mcdonnell, J. A. M.↗

NASA NTRS1987

Comet Sugano-Saigusa-Fujikawa (1983V) - A small, puzzling comet

Spectroscopic and infrared observations of Comet Sugano-Saigusa-Fujikawa (1983V) were obtained during its close approach to the earth on June 11-14, 1983. The forbidden O I production rates of 1.8 + or - 0.9 x 10 to the 26th atoms/s observed on June 12.3 and 7 + or - 3.5 x 10 to the 26th atoms/s on June 13.4 lead to derived water-production rates of 3 x 10 to the 27th mol/s on June 12 and 1.1 x 10 to the 28th mol/s on June 13. The abundances of the minor species NH2, CN, C2, and C3 are unusually low relative to forbidden O I. The upper limit to the average nuclear radius from infrared and visual photometry on June 12-13 (assuming that the entire signal came from the nucleus) is about 370 m. The dust/gas mass ratio was less than 0.01 on June 12 and less than 0.005 on June 13.

Hanner, M. S.↗

NASA NTRS1986

Mass distribution of particulates measured by Giotto's Dust Impact Detection System (DIDSY) in the close encounter period

The cumulative mass distribution of the comet Halley dust efflux in the close encounter period -300 to +300 sec was analyzed. Analysis of the cumulative mass distribution index (alpha) shows considerable short time scale variation. There is clear evidence from the flux rates of passage through at least one major dust enhancement (dust jet) just after closest approach and this is associated with a steepening of the alpha. Comparison with measurements from other sources, and with preencounter predictions, is also made.

Zarnecki, J. C.↗

NASA NTRS1986

The NASA infrared telescope facility Comet Halley monitoring program. I - Preperihelion results

The 1-20 microns IR monitoring program for Comet Halley whose results are presented covered January 1985 to January 1986, using a 7-arcsec aperture. It is noted that the comet's dust production was about 6 million g/s at a heliocentric distance of 1 AU; the albedo of the dust in the coma was 3-4 percent. These results are compared with those for previously observed comets.

Tokunaga, A. T.↗

NASA NTRS1986

Infrared photometry of periodic comets

18 comets, ranging in helicentric distance from 1 to 5 AU were observed with the NASA IRTF. Highlights for 1985-86 include: (1)Halley was detected 1/85 and 3/85 at R = 5 and 4.5 AU; (2) Regular Halley monitoring program was set up in collaboration with IRTF staff; (3)Nucleus of Arend-Rigaux was detected, light curve observed (0.6 m amplitude at 10 microns) and radius derived (5 km); (4)Dust coma of Giacobini-Zinner was observed at time of ICE encounter; and (5)Mapping of the thermal emission spectrum simultaneously with the S/C encounters is scheduled for March 1986.

Hanner, M. S.↗

NASA NTRS1986

Thermal emission from the dust coma of Comet Bowell and a model for the grains

An analysis of the physical characteristics of Comet Bowell is presented based on 10 and 20 microns emissions observed with the NASA 3 m IR telescope during 1981-82. Numerical models are defined for quantifying the number of dust particles at a given radius and at a given angular distance from the nucleus, the contribution of icy grains to the 20 microns flux and the average albedo, and the dust distribution in the coma. Large, dirty ice grains are judged to be responsible for production of OH at a rate of about 10 to the 29th mol/sec during the spring of 1981. The total surface area of the dirty ice grains is projected to be 10 to the 15th sq cm. The coma in 1982 would therefore have consisted of nonvolatile grains, i.e., old dirty ice grains. Further observations of other, similar comets are needed to identify the composition of the emitted grains and the heliocentric distance at which high water production is initiated.

Hanner, M. S.↗

NASA NTRS1986

Dust density and mass distribution near comet Halley from Giotto observations

The density and the mass spectrum of the dust near comet Halley have been measured by the Giotto space probe's dust impact detection system. The dust spectrum obtained at 291,000 km from the comet nucleus show depletion in small and intermediate masses; at about 600 km from the nucleus, however, the dust activity rises and the spectrum is dominated by larger masses. Most of the mass striking Giotto is noted to reside in the few large particles penetrating the dust shield. Momentum balances and energy considerations applied to an observed deceleration suggest that a large mass of the spacecraft was detached by an impact.

Mcdonnell, J. A. M.↗

NASA NTRS1986

The Comet Halley dust and gas environment

Quantitative descriptions of environments near the nucleus of comet P/Halley have been developed to support spacecraft and mission design for the flyby encounters in March, 1986. To summarize these models as they exist just before the encounters, the relevant data from prior Halley apparitions and from recent cometary research are reviewed. Orbital elements, visual magnitudes, and parameter values and analysis for the nucleus, gas and dust are combined to predict Halley's position, production rates, gas and dust distributions, and electromagnetic radiation field for the current perihelion passage. The predicted numerical results have been useful for estimating likely spacecraft effects, such as impact damage and attitude perturbations. Sample applications are cited, including design of a dust shield for spacecraft structure, and threshold and dynamic range selection for flight experiments. It is expected that the comet's activity may be more irregular than these smoothly varying models predict, and that comparison with the flyby data will be instructive.

Divine, N.↗

NASA NTRS1986

The nature of cometary grains from remote sensing

Physical property data of cometary grains are derived primarily from thermal emission measurement and optical scattering. Results consistent with the properties of micrometeorites collected in the stratosphere are described.

Hanner, M. S.↗

NASA NTRS1986

Cosmic dust and space debris; Proceedings of the Topical Meetings and Workshop 6 of the 26th COSPAR Plenary Meeting, Toulouse, France, June 30-July 11, 1986

These proceedings encompass topics in the fields of extraterrestrial material samples, IRAS solar system and dust model results, and earth orbit debris. Attention is given to chemical fractionation during high velocity impact, particle deceleration and survival in multiple thin foil targets, and IRAS studies of asteroids, comets, cometary tails, the zodiacal background, and the three-dimensional modeling of interplanetary dust. Also discussed are the evolution of an earth orbit debris cloud, orbital debris due to future space activities, collision probabilities in geosynchronous orbits, and a bitelescopic survey of low altitude orbital debris.

Mcdonnell, J. A. M.↗

NASA NTRS1985

Dark grains in comet Crommelin

Comet P/Crommelin (1983n) was observed at 1-20 microns at the NASA IRTF March 29-April 1, 1984. The thermal emission spectrum fits a black body of about 290 K, cooler than other comets observed at 1 AU. The ratio of thermal to scattered radiation indicates that these grains were extremely dark with a geometric albedo of about 0.015 at J(1.25 microns) and 0.02 at K(2.25 microns). The 10 micron flux distribution on April 1 was very asymmetric, decreasing rapidly on the sunward side, less than 6000 km from the nucleus, and extended in the north and east. The spatial distribution and photometric data suggest that large grains emitted from the nucleus at very low velocity were viewed.

Hanner, M. S.↗

NASA NTRS1985

The dust coma of periodic Comet Churyumov-Gerasimenko (1982 VIII)

IR emission from the dust comet of Comet C-G was monitored at 1-20 microns with the 3-m NASA Infrared Telescope Facility at Mauna Kea, Hawaii during its perihelion passage from September 1982 to March 1983. The maximum dust production rate of approximately 200,000 g/sec was found to occur approximately one month after perihelion. It was also found that no obvious 1-micron silicate feature was present at 1.33 AU preperihelion, and that the ratio of dust/gas production was higher in other short-period comets observed in the infrared, particularly preperihelion. The low albedos derived for the dust grains (less than 0.05 micron) are noted to be plausible for mineral mixtures expected in cometary grains.

Hanner, M. S.↗

NASA NTRS1985

Does comet P/Arend-Rigaux have a large dark nucleus?

The first infrared observations of the comet P/Arend-Rigaux are presented. These indicate that both the reflected solar radiation and the thermal emission from the nucleus have been detected. From the observations, a geometric albedo as low as 5 percent and an average radius of 4.8 km for the nucleus are derived.

Tokunaga, A. T.↗

NASA NTRS1985

Infrared spectrophotometry of Comet IRAS-Araki-Alcock (1983d) - A bare nucleus revealed?

Spectra of the central core and surrounding coma of Comet IRAS-Araki-Alcock (1983d) were obtained at 8-13 microns on May 11 and 2-4 microns on May 12, 1983. Spatially resolved measurements at 10 microns with a 4-arcsec beam showed that the central core was more than 100 times brighter than the inner coma only 8 arcsec away; for radially outflowing dust, the brightness ratio would be a factor of 8. The observations of the central core are consistent with direct detection of a nucleus having a radius of approximately 5 km. The temperature of the sunlit hemisphere was greater than 300 K. Spectra of the core are featureless, while spectra of the coma suggest weak silicate emission. The spectra show no evidence for icy grains. The dust production rate on May 11.4 was about 100,000 g/sec, assuming that the gas flux from the dust-producing areas on the nucleus was about 0.00001 g/sq cm per sec.

Hanner, M. S.↗

NASA NTRS1985

A preliminary look at the dust in Comet Halley

Highlights of infrared observations of the dust are discussed and compared with first results from the space probes. An emission feature was detected at 3.4 microns; the 10 and 20 micron silicate features were well-observed; and far-infrared data out to 160 micron were obtained. Organic material seems to be abundant in grains and may explain the 3.4 micron emission. Calculations are presented for one example of organic material. A component of the grains may volatize at temperatures around 300 K.

Hanner, M. S.↗

NASA NTRS1984

JHK photometry of Comet Bowell (1982I)

Comet Bowell (1982I) was observed at JHK (1.25, 1.68, 2.25 microns) with the NASA Infrared Telescope Facility on March 10, 1981, June 3-5, 1981, and February 22, 1982. The inner coma was no brighter near perihelion in February 1982 than it was in 1981. Total area x albedo of the grains within 10,000 km of the nucleus was about 5 x 10 to the 12th/sq cm.

Hanner, M. S.↗