Engineering topics

Mitchell, D. L.

Publications and source records attributed to Mitchell, D. L..

39 records · Page 3

NASA NTRS1987

Evidence for chain molecules enriched in carbon, hydrogen, and oxygen in comet Halley

In situ measurements of the composition and spatial distribution of heavy thermal positive ions in the coma of comet Halley were made with the heavy-ion analyzer RPA2-PICCA aboard the Giotto spacecraft. Above 50 atomic mass units an ordered series of mass peaks centered at 61, 75, 91, and 105 atomic mass units were observed. Each peak appears to be composed of three or more closely spaced masses. The abundances decrease and the dissociation rates increase smoothly with increasing mass. These observations suggest the presence of chain molecules that are enriched in carbon, oxygen, and hydrogen, such as polyoxymethylene (polymerized formaldehyde), in comet Halley.

Mitchell, D. L.↗

NASA NTRS1986

Radial variations of flow parameters and composition of cold heavy ions within 50,000 km of Halley's nucleus

Composition and flow parameter of cold heavy ions from the PICCA instrument on Giotto within a cometocentric distance of 50,000 km are presented. A distinct boundary at about 27,000 km, where the flow parameters changed abruptly, is identified and its physical significance is discussed. Radial profiles of heavy ion groups and abundance ratios are given.

Korth, A.↗

NASA NTRS1986

Derivation of heavy (10-210 AMU) ion composition and flow parameters for the Giotto PICCA instrument

The Giotto heavy ion analyzer RPA2-PICCA was designed to identify the composition and distribution of heavy thermal positive ions in the coma of comet Halley. The instrument is an electrostatic analyzer which takes advantage of the large relative flyby velocity and the fact that the ions in the inner coma should be cold and predominantly singly charged. A method of deconvolving E/Q measurements to yield ion mass composition, temperature, and flow velocity is presented. The measurements are used to investigate the dynamic behavior of the ions and variations in mass composition as a function of cometary distance.

Mitchell, D. L.↗