Model for comet-solar wind interaction.
Comet-solar wind interaction model, determining contact discontinuity size and shape around comet nucleus and ion specular reflection
Shelby, M. E.↗
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Infrared Measures of Comets
Infrared observations of two comets, 1969g and 1969i, are presented. In both comets the infrared flux appears to be of thermal origin. The structure of the sources as well as the temperature, emissivity, and composition of the radiating material are discussed.
Lee, T.↗
Photometry of comets
The photometric observations of comets are discussed in terms of providing profiles of the whole comet.
Miller, F.↗
Spectroscopic observations of comets
The value of C-12/C-13 for the Comets Tago-Sato-Kosaka and Bennett was investigated. The values for both comets are presented in spectrographs.
Owen, T. C.↗
Present Understanding of Comets
An assessment of cometary research from 1970 to 1972 was made. Particular attention was given to the Lyman alpha halo of Comets Tago-Sato-Kosaka, Bennett, and Encke, and the large gas productions of these comets. The icy conglomerate and sand bank models are discussed in detail.
Delsemme, A. H.↗
Photographic Observations of Comet Bennett, 1970II
Direct photography of Comet Bennett with a range of focal lengths shows structure in the coma and strong Type 1 and Type 2 tails. The Type 1 tail shows motion in 15 minutes. The inner coma contains spiral-shaped jets of a type observed visually on occasion in the past but not photographed before. The spiral shape is apparently due to the rotation of the nucleus. On the assumption that the outward velocity of the jets is 0.6 km/sec, as estimated by Delsemme, a rotation period of 1.4 to 1.5 days is derived for the nucleus. The rotation is direct (in the sense of the comet's orbital motion).
Larson, S. M.↗
A model of the physical properties of comet Encke
The available observational data on periodic comet Encke were collected and interpreted in order to construct a model of the comet. The model is intended for use in the design of scientific experiments and spacecraft systems to be used on future missions to Encke. Numerical values and ranges of uncertainty are given for all of the important structural, compositional, and photometric parameters with references to the original research from which these were calculated or estimated.
Taylor, F. W.↗
Photographic observations of Comet Bennett, 1970II.
Direct photography of Comet Bennett with a range of focal lengths shows structure in the coma and strong Type I and Type II tails. The Type I tail shows motion in 15 minutes. The inner coma contains spiral-shaped jets of a type observed visually on occasion in the past but not photographed before. The spiral shape is apparently due to the rotation of the nucleus. On the assumption that the outward velocity of the jets is 0.6 km/sec, as estimated by Delsemme, a rotation period of 1.4-1.5 days is derived for the nucleus. The rotation is direct (i.e., in the sense of the comet's orbital motion).
Larson, S. M.↗
Implications of current SEP mission performance data on planning exploration of comets and asteroids.
The most comprehensive performance data base currently available for SEP comet and asteroid rendezvous missions has been synthesized and reduced into forms allowing evaluation of primary mission planning parameters. These data are based on utilization of the Shuttle with a Centaur injection stage and a SEP system having a 3000-sec specific impulse. The analysis indicates that a SEP vehicle system designed at a power level of around 20 kW with a system operating life of three years, offers the capability for achieving rendezvous missions to almost all comet and asteroid targets expected to be of interest in the 1980s. This degree of mission selection flexibility is desirable for a comprehensive program of small body exploration.
Allen, L. C.↗
Study of 1980 Comet Encke-asteroid missions using a spin-stabilized spacecraft. Volume 1: Summary report
As a contribution to improved understanding of early comet exploration options, independent studies were undertaken which resulted in the identification of a number of fast flyby mission options for the 1980 apparition of Encke. The primary impetus for this approach was the prospect of utilizing existing launch vehicles and conventional spacecraft technology. In addition, timely experience and scientific data gained through an early fast flyby could prove valuable in implementing more ambitious succeeding missions, including a flyby of Comet Halley in 1986.
Bursnall, W. J.↗
System definition for Cometary Explorer: A mission to intercept the comets Grigg-Skjellerup (1977) and Giacobini-Zinner (1979)
Its purpose was to define a low cost dual-comet intercept mission. The study established the framework for investigating future ballistic intercept missions to comets.
Source record↗
Airborne observations of methane in Comet Kohoutek
The experiment is described for airborne observations of Comet Kohoutek using an infrared tilting-filter photometer. Preliminary analysis of the data established an upper limit to the Comet's fluorescence radiation in methane lines at 3.3 microns.
Roche, A. E.↗
Polarimetric observations of Comet Kohoutek (1973f)
Radio, optical, and visual observations were made of Comet Kohoutek (1973f) using facilities of the National Radio Astronomy Observatory (NRAO) and of the Hawaii Night Sky Observatory, State University of New York at Albany (SUNYA). Transit observations were made using the NRAO 300 ft radio telescope on six consecutive days beginning November 24, 1973. Observations were carried out in the continuum at 11 cm using the 4-feed system at different position angles. The data were recorded on magnetic tape and were computer reduced. Results were negative, with an rms error of 62 milli flux units, giving an upper limit of 180 mfu for the 11 cm continuum emission from the Comet. This relatively high detection limit resulted from a combination of interference and bad weather that affected these pre-perihelion observations. No observations could be scheduled near or after perihelion.
Weinberg, J. L.↗
Study of ballistic mode comet Encke mission opportunities
An analysis was conducted of the space mission to intercept the comet Encke. The two basic types of flight geometry considered for the mission are described. The primary interactions between time-of-flight and performance characteristics are displayed. The representative spacecraft characteristics for the Titan 3/Centaur launch vehicle are tabulated. The navigation analyses for the two missions are developed to show: (1) assessment of the navigation feasibility of the missions, (2) determination of the total velocity budget for the trim maneuvers, and (3) evaluation of dispersions at comet encounter.
Hollenbeck, G. R.↗
Spectrophotometry of comets
Photoelectric spectrophotometric- and image tube equipped spectrographic-studies on comets are used to formulate a new model for the cometary nucleus that is physically similar to the icy-conglomerate. Absolute flux distributions of the principal spectral features for five comets of different compositions and heliocentric distances were evaluated. Comparison of visible and infrared brightnesses was used to calculate the optical albedos of observed particles.
Odell, C. R.↗
Interaction effects between solar wind and comet Bennett
Observations of the solar wind and the comet Bennett made during the period from Mar. 23 to Apr. 5, 1970 are considered. During this period the position of the comet had been comparatively close to earth at a distance of about 0.7 AU. Plasma data from four space probes and photographs of a number of observatories are taken into account. The relation between a sudden change in the velocity of the solar wind and the occurrence of a pronounced disturbance in the cometary tail is investigated.
Burlaga, L. F.↗
Behaviour of comet Kohoutek /1973f/
The spectral identification of CH3CN and HCN provides the first support for the hypothesis first proposed by Wurm (1943), of chemically stable 'parent molecules' for the less stable radicals and ions seen in the coma and the tail. These two molecules were among the earliest discovered in dense interstellar clouds. Circumstantial evidence for the presence of water as the dominant volatile component in the nucleus has been growing for some time. However, a much more volatile species is required to explain the observed behavior of the comet. CO, formaldehyde, or methane would quickly evaporate as the comet approached the sun.
Mendis, D. A.↗
Optical image of a cometary nucleus: 1980 flyby of Comet Encke
The feasibility was investigated of obtaining optical images of a cometary nucleus via a flyby of Comet Encke. A physical model of the dust cloud surrounding the nucleus was developed by using available physical data and theoretical knowledge of cometary physics. Using this model and a Mie scattering code, calculations were made of the absolute surface brightness of the dust in the line of sight of the on-board camera and the relative surface brightness of the dust compared to the nucleus. The brightness was calculated as a function of heliocentric distance and for different phase angles (sun-comet-spacecraft angle).
Wells, W. C.↗