Search Publications
Pluto's extended atmosphere: An escape model and initial observations
Stern, S. A.; Clarke, John T.; Trafton, Laurence M.
We have calculated the rates of production and hydrodynamic outflow of atomic hydrogen resulting from the photodissociation of methane in the upper atmosphere of Pluto. Under the present near-perihelion conditions this yields an extended cloud of H around Pluto which is likely to be the most easily observable signature of Pluto's extended atmosphe…
Modeling of the thermal behavior and of the chemical differentiation of cometary nuclei
Schmitt, B.; Espinasse, S.; Klinger, J. +1 more
Taking into account the low values of average density reported for Comet P/Halley, a model of a porous comet nucleus has been developed. The model includes heat conduction through the solid matrix and heat and mass transfers due to the vapor phase circulating in the pore system. Sublimation and recondensation of volatile species within the nucleus…
Large dust particles along the Giotto trajectory
Keller, H. U.; Curdt, W.
Images of Comet Halley taken by the Halley Multicolour Camera (HMC) onboard ESA's Giotto spacecraft provide highly accurate information on the viewing direction. As a part of the spacecraft dynamical system, HMC was very sensitive to attitude variations that occurred during the final approach phase. HMC identified several discrete events that were…
Overview of recent analysis of the energetic particle observations recorded in Situ by the EPONA instrument on the Giotto Mission to Comet Halley
Neubauer, F. M.; Daly, P.; McKenna-Lawlor, S. M. P. +4 more
Highlights of recent results obtained through analyzing data recorded by the energetic particles experiment EPONA on the Giotto Mission to Comet Halley (March 12-15, 1986) from ∼7 × 10 6 km upstream of the bow shock (inbound) to ∼6 × 10 6 km upstream of the bow shock (outbound) are presented. The identities of the ions record…
The 2.5-12 µm spectrum of comet halley from the IKS-VEGA experiment
Bibring, J. -P.; Encrenaz, T.; Crovisier, J. +14 more
The infrared instrument IKS flown on board the VEGA space probes was designed for the detection of emission bands of parent molecules, and for a measurement of the size and temperature of the thermal emitting nuclear region. The instrument had three channels with cooled detectors: an "imaging channel" designed to modulate the signal of the nucleus…
The relationship of active comets, ``extinct'' comets, and dark asteroids
Cruikshank, D. P.; Tholen, D. J.; Hartmann, W. K.
Spectrophotometric data on groups of asteroids in different types of orbits reveal different distributions of spectral properties, depending on whether the orbits are cometary or noncometary. In a list of 10 asteroids frequently suggested on purely dynamical grounds to be extinct or dormant comets, all have properties suggestive of spectral classe…
Ultraviolet spectrophotometry of comet Giacobini-Zinner during the ICE encounter
Feldman, P. D.; A'Hearn, M. F.; Schleicher, D. G. +8 more
A program of ultraviolet spectrophotometry using the International Ultraviolet Explorer (IUE) Observatory was carried out in support of the International Cometary Explorer (ICE) mission. The H 2O production rate was monitored from 1985 June to October. Between 1985 September 9 and 12, the spatial and temporal variation and abundance (or…
The Jovian stratosphere in the ultraviolet
Encrenaz, T.; Owen, T.; Caldwell, J. +3 more
The center-of-disk reflectivity of Jupiter in the wavelength range from 1450 to 3150A˚has been computed from 30 low-dispersion IUE spectra taken during solar maximum in 1978-1980. A vertically inhomogeneous radiative transfer program is used to compute model reflectivities of various stratospheric compositions for comparison. Ammonia and acetylene…