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In situ gas and ion measurements at comet Halley
Berthelier, J. J.; Eberhardt, P.; Krankowsky, D. +9 more
The neutral mass spectrometer experiment (NMS) carried by the Giotto spacecraft was designed to determine the abundances and the chemical, elemental and isotopic composition of the gases and low-energy ions in the coma of comet Halley. Its first results show the predominance of water vapour (~80% by volume). Preliminary evaluation of the data yiel…
Ion composition and dynamics at comet Halley
Schwenn, R.; Altwegg, K.; Balsiger, H. +16 more
The ion mass spectrometer aboard the Giotto spacecraft measured the composition and velocity distributions of cometary ions at distances of ~7.5×l06 to ~1,300 km from the nucleus of comet Halley. Well outside the bow shock, pick-up cometary H+ ions were found in a diffuse shell-like distribution. Heavier ions (C+, …
First results from the Giotto magnetometer experiment at comet Halley
Neubauer, F. M.; Glassmeier, K. H.; Pohl, M. +9 more
The Giotto magnetometer experiment at comet Halley has for the first time provided magnetic field measurements in all the important spatial regions characterizing the front-side interaction between the solar-wind magnetoplasma and a cometary atmosphere. Upstream waves of cometary origin have been observed at distances of >2×106 km fr…
First Halley Multicolour Camera imaging results from Giotto
Wilhelm, K.; Keller, H. U.; Barbieri, C. +15 more
The first imaging results from the Halley Multicolour Camera (HMC) during the Giotto fly-by of comet Halley provide images centred on the brightest part of the inner coma which show the silhouette of a large, solid and irregularly shaped cometary nucleus and jet-like dust activity visible in reflected sunlight. A first assessment of the data yield…
Composition of comet Halley dust particles from Giotto observations
Hornung, K.; Kissel, J.; Sekanina, Z. +16 more
Mass spectra of cometary dust particles measured by the PIA dust particle analyser aboard the Giotto spacecraft show some unexpected and striking features. First, small particles below 10-14 g are much more abundant than anticipated by models. Second, most of the particles are rich in light elements such as H, C, N and O, suggesting the…
Cometary Grain Scattering versus Wavelength, or, ``What Color Is Comet Dust?''
Jewitt, David; Meech, Karen J.
Optical and near-infrared observations of comets are combined in a systematic study of the wavelength dependence of the scattering from cometary grains. The normalized rate of change of the reflectivity of cometary grains with respect to the wavelength of observations decreases as the wavelength increases. The observed wavelength dependence of the…
Rotational period of comet Halley
Schleicher, D. G.; Millis, R. L.
The rotational period of the nucleus of comet Halley is a basic datum which must be accurately known if the vast collection of observations of this comet recently obtained from spacecraft and ground-based observatories are to be correctly interpreted. Sekanina and Larson, who have studied the morphology of the comet's coma, find a period near 2.2 …
The Giotto encounter with comet Halley
Reinhard, R.
The Giotto spacecraft encountered comet Halley on 14 March 1986, approaching to within ~600km of the nucleus. Its scientific payload comprised ten hardware experiments: a narrow-angle camera, three mass spectrometers (for neutrals, ions and dust), various dust detectors a photopolarimeter and a set of plasma experiments. All experiments performed …
Dust density and mass distribution near comet Halley from Giotto observations
Grün, E.; Zarnecki, J. C.; Wallis, M. K. +25 more
The dust impact detection system (DIDSY) carried by the Giotto spacecraft has measured the density and mass spectrum (in the range 10-20-10-8 kg) of the dust near comet Halley. Profiles of the dust spectrum obtained at a distance of 291,000 km from the Halley nucleus show a complex mass spectrum, depleted in intermediate and …
Ion flow at comet Halley
Cerulli-Irelli, R.; Thomsen, M.; Johnstone, A. +25 more
The three-dimensional positive ion analyser aboard the Giotto spacecraft has been used to study the interaction between protons and α-particles in the solar wind and positive ions from comet Halley. Although the first impression of the overall structure is that the plasma flow evolves smoothly as the nucleus is approached, three sharp transitions …