Search Publications
The nucleus of comet Halley: Surface structure, mean density, gas and dust production
Rickman, H.
The relation between the mass of a cometary nucleus, its gas production curve, the mean outflow velocity, and the nongravitational delay of the comet is discussed, emphasizing the properties of gaseous outflow from comet Halley. The importance of knowledge about the rotational state of the nucleus is stressed, and it is argued that the likely wobb…
Complex organic ions in the atmosphere of Comet Halley
Anderson, K. A.; Reme, H.; Korth, A. +7 more
The ordered series of broad mass groups observed in thermal ion mass spectra taken in the coma of Comet Halley by the RPA2-PICCA instrument aboard the Giotto spacecraft is shown to be characteristic of molecules rich in hydrogen, carbon, nitrogen, and oxygen, and does not imply the presence of a long chain polymer such as polyoxymethylene. Inside …
In situ exploration of the dusty coma of comet P/Halley at Giotto's encounter: Flux rates and time profiles from 10-19kg To 10-5kg
Green, S. F.; Kissel, J.; McDonnell, J. A. M. +4 more
Flux rates and time profiles from the Giotto DIDSY and PIA experiments are presented in the light of more refined data analysis and increased data coverage. The methods of data analysis for both experiments are explained, together with the relevant behaviour of their in-flight performance. A mass distribution from 237 000km to 11 500km from comet …
Mechanisms of dust emission from the surface of a cometary nucleus
Spohn, T.; Thiel, K.; Krankowsky, D. +9 more
Cometary nuclei consist of mixtures of ices and non-volatile particulates in mass proportions of similar magnitudes. Dust is carried by the gas drag of the sublimating ices. Gas drag from free expansion of the gases from the nucleus dominates the acceleration of dust particles after their release from the surface. Significant gas pressure can buil…
Time-dependent study of magnetic fields in comets giacobini-zinner and halley
Neubauer, F. M.; Huebner, W. F.; Slavin, J. A. +4 more
Stationary MHD models are used to analyze the data of magnetic field measurements in comets Giacobini-Zinner and Halley. The contributions of the draping, of changes in the IMF, and of turbulence are separated and extended patches of unidirectional field regions are identified. A time-dependent MHD simulation of the nonstationary flow following a …
Experimental plasma parameters at comet Halley
Amata, E.; Formisano, V.; Wilken, B. +3 more
Bulk speed, density and temperature of the plasma are computed for protons and water-group ions in comet P/Halley using data from the two ion sensors of the JPA experiment flown on Giotto. Two water group ion populations, locally generated and implanted further upstream, evolve with different density and temperature during the fly-by. The centre o…
Carbonaceous materials as components of cometary dust
Colangeli, L.; Fonti, S.; Bussoletti, E. +4 more
Recent exploration of comet Halley by space missions and ground-based observations have allowed to acquire a large amount of new information on cometary materials. In particular, IR spectroscopy has evidenced two pronounced and structured emission features at around 3.28 and 3.37 µm. Different kinds of gaseous molecules and/or solid grains i…
Identification of surface features on comet P/Halley
Keller, H. U.; Reitsema, H. J.; Delamere, W. A.
The Giotto Halley Multicolour Camera obtained images of P/Halley that resolved the nucleus, showing active regions and other features on the surface. At least twenty-one discrete bright features can be identified in the images, and eight distinct regions associated with morphological characteristics can be recognized. The projected limb is approxi…
In situ exploration of the dusty coma of comet P/Halley at Giotto's encounter: Nucleus emission and production rates from temporal variability
McDonnell, J. A. M.; Pankiewicz, G. S.; Perry, C. H.
Flux-time profiles from the DIDSY and PIA experiments, taken at Giotto's encounter with comet P/Halley, are used to study coma dust dynamics and the nucleus emission. A comparison of the data with a `fountain' model, incorporating variable source function and grain type is made. Local enhancements such as jets, envelopes and terminators are analys…
Giotto Comet Halley Dust Impact experiment: Studies of discrete impact events
McDonnell, J. A. M.; Alexander, W. M.; Goad, H. +2 more
Analysis of discrete pulse height data from specific individual events of the Giotto Comet Halley Dust Impact Detectors DID-1 and DID-4 has been completed. The cumulative flux for the mid-size range of this Giotto comet dust experiment has been studied and results are presented. The technique employed in the investigation utilized a constant numbe…