Engineering topics

Mumma, Michael J.

Publications and source records attributed to Mumma, Michael J..

58 records · Page 4

NASA NTRS1986

Velocity-resolved observations of water in Comet Halley

An infrared spectrum of comet Halley was recorded at the Kuiper Airborne Observatory with an instrumental velocity resolution of 1.1 km/sec. A total of 13 emission lines in the 2.65 micron spectral region were assigned to neutral gaseous H2O : 10 in the 001 to 000 band and 3 in the hot 011 to 010 band. The position and widths of these lines are functions of the gas velocity field in the coma. Analysis indicates that the neutral gas outflow is widely dispersed about the nucleus. This spectroscopic picture is consistent with spacecraft images that show multiple jets releasing material into most of the sunfacing hemisphere.

Larson, Harold P.↗

NASA NTRS1986

The ortho/para ratio of water vapor in Comet Halley

The ortho/para ratio of H2O is shown to be an invariant in the cometary coma. The dependence of ortho-para ratio on temperature in thermal equilibrium is given, and the nuclear-spin-temperature is defined. Its relation to the physical temperature of the cometary ices is discussed, and the prospects for using the observed ortho/para ratio to infer properties of the cometary nucleus are explored. The ortho/para ratio in Halley's comet is derived from high resolution infrared spectra of near 2.7 microns wavelength. On UT December 24.1, 1985 it was 2.73 + or - 0.17, and on UT March 22.7, 1986 it was 3.23 + or - 0.37. The nuclear-spin-temperature was 35 K (+9 K, -5 K) pre-perihelion, and less than 40 K post-perihelion, at the 67% confidence limit. Both numbers are consistent with modeled values of the equilibrium temperature of the cometary nucleus at aphelion (47 K). However, at the 95% confidence limit they are also fully consistent with temperatures less than 50 K, corresponding to an ortho/para ratio of about 3.0.

Mumma, Michael J.↗

NASA NTRS1986

Velocity-resolved observations of water in comet Halley

High-resolution observations of H2O in comet Halley are presented. The positions and widths of the H2O emission line profiles are indicative of the coma's velocity field characteristics. Spectral line shape changes are used to infer temporal variations in the kinematic properties of the outflow. The results suggest that H2O is released into the coma by way of multiple jets.

Larson, Harold P.↗

NASA NTRS1986

Velocity-resolved observations of water in Comet Halley

High resolution (lambda/delta lambda approx. = 3 x 10 to the 5th power) near-infrared observations of H2O emission from Comet Halley were acquired at the time of maximum post-perihelion geocentric Doppler shift. The observed widths and absolute positions of the H2O line profiles reveal characteristics of the molecular velocity field in the coma. These results support H2O outflow from a Sun-lit hemisphere or the entire nucleus, but not from a single, narrow jet emanating from the nucleus. The measured pre- and post-perihelion outflow velocities were 0.9 + or - 0.2 and 1.4 + or - 0.2 km/s, respectively. Temporal variations in the kinematic properties of the outflow were inferred from changes in the spectral line shapes. These results are consistent with the release of H2O into the coma from multiple jets.

Larson, Harold P.↗