Exploration of Halley's Comet

The 1985/86 apparition of Halley's Comet turned out to be the most important apparition of a comet ever. It provided a worldwide science community with a wealth of exciting new discoveries, the most remarkable of which was undoubtedly the first image of a cometary nucleus. Halley's Comet is the brightest periodic comet, and the most famous of the 750 known comets. With its 76-year period, its recent appearance was truly a "once-in-a-lifetime" observational opportunity. The 1985/86 apparition was the thirtieth consecutive recorded apparition. Five apparitions ago, the English astronomer Edmond Halley discovered the periodicity of "his" comet and correctly predicted its return in 1758, a triumph for science best appreciated in the context of contemporary views, or rather fears, about comets at that time. The increasingly rapid progress in technological development is very much apparent when one compares the dominant tools for cometary research during Halley's next three apparitions: in 1835 studies were made based on drawings ofthe comet; in 1910 photographic plates were used; while in March 1986 an armada of six spacecraft from four space agencies approached the comet and carried out in situ measurements, 1 AU from the Earth. In 1910, nobody could have dreamed that this was possible, and today it is equally difficult to anticipate what scientists will be able to achieve in 2061.

New information on comet P/Halley as depicted by Giotto di Bondone and other Western artists.- Encounters with comets: discoveries and puzzles in com-etary plasma physics.- The pick-up of cometary protons by the solar wind.- Alfvénic turbulence in the solar wind flow during the approach to comet P/Halley.- General features of comet P/Halley: solar wind interaction from plasma measurements.- The Sakigake/Suisei encounter with comet P/Halley.- Waves in the magnetic field and solar wind flow outside the bow shock at comet P/Halley.- Solar wind flow through the comet P/Halley bow shock.- Macroscopic perturbations of the IMF by P/Halley as seen by the Giotto magnetometer.- Low-frequency magnetic field fluctuations in comet P/Hal-ley’s magnetosheath: Giotto observations.- Fine structure of the magnetic field in comet P/Halley’s coma.- Giotto magnetic-field results on the boundaries of the pile-up region and the magnetic cavity.- Identification of boundaries in the cometary environment from ac electric field measurements.- Dust observations of comet P/Halley by the plasma-wave analyzer.- Comparative study of the low-frequency waves near comet P/Halley during the Vega-1 and Vega-2 fly by s.- Plasma flow in the cometosheath of P/Halley during the encounter of Suisei.- MHD waves detected by ICE at distances ?28 106 km from comet P/Halley: Cometary or solar wind origin?.- Plasma-tail activity at the time of the Vega encounters.- Observations of cometary plasma-wave phenomena.- Hydromagnetic waves associated with cometary water group ions: Sakigake observation.- Plasma properties from the upstream region to the cometo-pause of comet P/Halley: Vega observations.- Observations of heavy energetic ions far upstream from comet P/Halley.- Spatial distribution of water-group ions near comet P/Hal-ley observed by Suisei.- An interpretation of the ion pile-up region outside the ionospheric contact surface.- Description of the main boundaries seen by the Giotto electron experiment inside comet P/Halley-solar wind interaction region.- In-situ observations of a bi-modal ion distribution in the outer coma of comet P/Halley.- The composition and radial dependence of cometary ions in the coma of comet P/Halley.- Pick-up ions at comet P/Halley’s bow shock: observations with the IIS spectrometer on Giotto.- Ion temperature and flow profiles in comet P/Halley’s close environment.- The composition and dynamics of cometary ions in the outer coma of comet P/Halley.- Expansion velocity and temperatures of gas and ions measured in the coma of comet P/Halley.- Giotto-IMS observations of ion-flow velocities and temperatures outside the magnetic cavity of comet P/Halley.- The dependence of mass resolution and sensitivity of the PUMA instrument on the energy spread of ions produced by hypervelocity impacts.- Spatial distribution of heavy ions in comet P/Halley’s coma.- Quasi-periodic features and the radial distribution of cometary ions in the cometary plasma region of comet P/Halley.- Electronic spectroscopy and relaxation of some molecular cations of cometary interest.- Possible models on disturbances of the plasma tail of comet Halley during the 1985–1986 apparition.- Structure and dynamics of the plasma tail of comet P/Halley. I. Knot event on December 31,1985.- Structure and dynamics of the plasma tail of comet P/Halley. II. Kink event on January 10–11,1986.- Hot ions observed by the Giotto ion mass spectrometer at the comet P/Halley contact surface.- Photographic observations of tail-formation activities of comet P/Halley in November 1985.- The outburst of comet P/Halley on December 12,1985.- Structure and dynamics of plasma-tail condensations of comet P/Halley 1986 and inferences on the structure and activity of the cometary nucleus.- Observations of the coma of comet P/Halley and the outburst of 1986 March 24–25 (UT).- Observations of ions in comet P/Halley with a focal reducer.- Two disconnection events in comet P/Halley and possible solar causes.- Activity of the plasma tail of comet P/Halley in March 1986.- The cause of two plasma-tail disconnection events in comet P/Halley during the ICE-Halley radial period.- Energy spectra of energetic ions in the vicinity of comet P/ Giacobini-Zinner.- Plasma structures in comets P/Halley and Giacobini-Zinner.- Analysis of the electron measurements from the Plasmag-1 experiment on board Vega-2 in the vicinity of comet P/Halley.- The upstream regionforeshock and bow shock wave at comet P/Halley from plasma electron measurements.- Stochastic Fermi acceleration of ions in the pre-shock region of comet P/Halley.- Measurements of low energy electrons and spacecraft potentials near comet P/Halley.- Charge exchange of solar wind ions in the coma of comet P/Halley.- Fluid simulation of comet P/Halley’s ionosphere.- Unusual characteristics of electromagnetic waves excited by cometary newborn ions with large perpendicular energies.- Far-ultraviolet objective spectra of comet P/Halley from sounding rockets.- IUE observations of comet P/Halley: evolution of the ultraviolet spectrum between September 1985 and July 1986.- Some diatomic molecules from comet P/Halley’s UV spectra near spacecraft flybys.- Activity of comet P/Halley on March 23–25,1986: IUE observations.- Cometary MHD and chemistry.- Atomic hydrogen production rates for comet P/Halley from observations with Dynamics Explorer 1.- The spectrum of P/Halley’s coma obtained with an objective-prism.- Comet P/Halley neutral gas density profile along the Vega-1 trajectory measured by the Neutral Gas Experiment.- Low-resolution maps of comet P/Halley in principal atomic and molecular species.- Pioneer Venus measurements of HOand C production in comet P/Halley near perihelion.- Anisotropy of the neutral gas distribution of comet P/Halley deduced from NGE/Vega-1 measurements.- The atomic carbon distribution in the coma of comet P/Halley.- Carbon-isotope ratio in PUMA 1 spectra of P/Halley dust.- Study of the isotopic features of Swan bands in comets.- Kinematic properties of the neutral gas outflow from comet P/Halley.- The spectrum of comet P/Halley between 0. 9 and 2. 5 ?m.- Anisotropic non-stationary gas flow dynamics in the coma of comet P/Halley.- Infrared investigation of water in comet P/Halley.- The ortho-para ratio of water vapor in comet P/Halley.- The 2.7 ?m water band of comet P/Halley: interpretation of observations by an excitation model.- Curves of growth of emission lines in cometary spectra. Implications for H2O and OH bands of comet P/Halley.- The D/H ratio in water from comet P/Halley.- Improved gas-kinetic treatment of cometary water sublimation and recondensation: application to comet P/Halley.- Detection of OH rotational emission from comet P/Halley in the far-infrared.- 18-cm wavelength radio monitoring of the OH radical in comet P/Halley (1982i).- 10. 7 GHz continuum observations of comet P/Halley.- Rotational structure of the (2,0) Phillips band of C2 in comet P/Halley.- OH radio observations of comet P/Halley.- Observations of HCN in comet P/Halley.- The CO and N2 abundance in comet P/Halley.- Resolution of the [OI] + NH2 blend in comet P/Halley.- A rotational-state population analysis of the high-resolution IUE observation of CS emission in comet P/Halley.- Search for methane in comet P/Halley.- Evidence for methane and ammonia in the coma of comet P/Halley.- Detection of parent molecules in comet P/Halley from the IKS-Vega experiment.- Detection of a new emission band at 2. 8 ?m in comet P/Halley.- Photometry of P/Halley (1982i).- Polarimetry of comet P/Halley: continuum versus molecular bands.- Photometric observations of comet P/Giacobini-Zinner.- Circular polarization near the nucleus of comet P/Halley.- Spectrophotometry of comet P/Halley. I. Fluxcolumn density and emission gradients within the coma in the emission bands and the continuum.- Spectrophotometry of comet P/Halley at wavelengths 275–710 nm from Vega-2.- The visual brightness behavior of P/Halley during 1981–1987.- The spectral behavior of P/Halley at large heliocentric distance in light of the Giotto/Vega results.- Periodicities in the light curve of P/Halley and the rotation of its nucleus.- Photometry of comet P/Halley at near post-perihelion phases.- Observations of comet P/Halley at minimum phase angle.- Chinese observations of comet P/Halley in China and abroad Gong.- Thermal infrared imaging of comet P/Halley.- Low resolution mapping of comet P/Halley in the near-infrared.- Infrared monitoring of comet P/Halley.- Airborne and groundbased spectrophotometry of comet P/Halley from 5–13 micrometers.- The near-infrared polarization and color of comet P/Halley.- The 3.2–3.6 ?m emission features in comet P/Halley: spectral identifications and similarities.- Airborne spectrophotometry of P/Halley from 16 to 30 microns.- Photometry of comet P/Halley from 40 to 160 microns.- Airborne spectrophotometry of P/Halley from 20 to 65 microns.- Comet P/Halley near-nucleus phenomena in 1986.- The sunward spike of Halleys comet.- Complex refractive index of grain material deduced from the visible polarimetry of comet P/Halley.- Infrared emission from P/Halley’s dust coma during March 1986.- The dust tail of comet P/Halley in April 1986.- Albedo maps of comets P/Halley and P/Giacobini-Zinner.- Polarimetry of grains in the coma of P/Halley. I. Observations.- Polarimetry of comet P/Halley.- Calibration of the DIDSY-IPM dust detector and application to other impact ionisation detectors on board the P/Halley probes.- Dust in comet P/Halley from Vega observations.- Properties of dust in comet P/Halley measured by the Vega-2 three-channel spectrometer.- Dust distribution of comet P/Halley’s inner coma determined from the Giotto Radio-Science Experiment.- The dust distribution within the inner coma of comet P/Halley (1982i): encounter by Giotto’s impact detectors.- The dust coma of comet P/Halley: measurements on the Vega-1 and Vega-2 spacecraft.- Spatial and mass distribution of low-mass dust particles (m interplanetary space.- Evaporating grains in P/Halley’s coma.- Comet P/Halley’s nucleus and its activity.- Electrostatic charging and fragmentation of dust near P/Giacobini-Zinner and P/Halley.- Evolution of comet P/Halley in early march 1986 as observed from Vega pictures.- The spatial distribution of dust jets seen during the Vega 2 flyby.- Temperature and size of the nucleus of comet P/Halley deduced from IKS infrared Vega-1 measurements.- Fine dust structures in the emission of comet P/Halley observed by the Halley Multicolour Camera on board Giotto.- Detailed analysis of a surface feature on comet P/Halley.- The cometary nucleus: current concepts.- Composition measurements and the history of cometary matter.- Modeling P/Halley before and after the encounters.- Post-perihelion brightening of comet P/Halley: Springtime for Halley.- P/Halley dust characteristics: a comparison between Orio-nid and Eta Aquarid meteor observations and those from the flyby spacecraft.- Radiation formation of a non-volatile comet crust.- Astrometric positions of comet P/Halley.- A new approach to investigations of the long-term motion of comet P/Halley.- High-order librations of Halley-type comets.- Dormant phases in the aging of periodic comets.- The dynamical lifetime of comet P/Halley.- Galactic tides affect the Oort cloud: an observational confirmation.- The P/Halley meteor showers in 1985–1986.- The spectra of meteors from comet P/Halley.- Meteoroids from comet P/Halley. The comet’s mass production and age.- The 1985 return of the Giacobinid meteor stream.- The meteor stream associated with comet P/Grigg-Skjel-lerup.- Meteor contribution by short-period comets.- Associations between ancient comets and meteor showers.- Supplement.- Exploration of Halley’s Comet: symposium summary.- The Giotto mission to Halley’s Comet.- The Vega mission to Halley’s Comet.- The Sakigake/Suisei missions to Halley’s Comet.- The International Cometary Explorer.- The International Halley Watch.