Pioneer 10 and Voyager observations of the interstellar medium in scattered emission of the He584 A and H Lya 1216 A lines

Technical Report · Sun Jan 01 04:00:00 EST 1984

OSTI ID:6094931

Shemansky, D E; Judge, D L; Jessen, J M

The combination of Pioneer photometric and Voyager spectrometric observations of EUV interstellar-interplanetary emissions in the region beyond 5 A was applied to a determination of atomic hydrogen and helium densities. These density estimates obtained from direct measurement of scattered radiation depend on absolute calibration of the instruments in the same way as other earlier determinations based on the same method. However, the spacecraft data were combined with daily full sun averages of the H Lyman 1216 A line obtained by the Solar Mesospheric Explorer satellite to obtain a measure of atomic hydrogen density independent of instrument absolute calibration. The method depends on observations of long and short term temporal variability of the solar line over a one year period, and the fact that the ISM is optically thick. The density estimates from preliminary work on these observations are H 0.12 cu cm and H .016 cu cm, giving a density ratio close to the cosmic abundance value in contrast to some earlier results indicating a depletion of atomic hydrogen. Estimates were obtained of galactic background emissions in the signals of both spacecraft.

• Research Organization: University of Southern California, Los Angeles (USA)
• OSTI ID: 6094931
• Report Number(s): N-84-34361; NASA-CR-173931
• Country of Publication: United States
• Language: English

Related Subjects

640105* -- Astrophysics & Cosmology-- Galaxies
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABUNDANCE
ELEMENTS
FLUIDS
GASES
HELIUM
HYDROGEN
INTERSTELLAR SPACE
LYMAN LINES
NONMETALS
PHOTOMETRY
PIONEER SPACE PROBES
RARE GASES
SOLAR FLUX
SPACE
SPACE VEHICLES
SPECTROSCOPY
TIME DEPENDENCE
VEHICLES
VOYAGER SPACE PROBES