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Extreme ultraviolet dayglow observations with a helium gas absorption cell
Author(s) -
Freeman Jay,
Paresce Francesco,
Bowyer Stuart,
Lampton Michael
Publication year - 1978
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/gl005i009p00787
Subject(s) - photometer , helium , extreme ultraviolet , daytime , physics , flux (metallurgy) , ultraviolet , line of sight , altitude (triangle) , radiation , absorption (acoustics) , wavelength , line (geometry) , atmospheric sciences , astronomy , astrophysics , optics , atomic physics , materials science , laser , geometry , mathematics , metallurgy
During the Apollo‐Soyuz Test Project, an extreme‐ultraviolet photometer with a cyclically operated helium gas absorption cell observed the daytime sky from an orbital altitude of 225 km. When the line of sight pointed more than 60° from the Sun, the instrument detected 2 to 70 rayleighs of flux scattered from neutral geocoronal helium at wavelengths from 504 to 584 Å. The instrument also detected other radiation in the band 500‐700 Å of similar spatial distribution to the helium flux, which was definitely not due to the He I 584 Å spectral line, and which has not been detected by previous experimenters in data from 400 km altitude. Possible sources of this radiation are discussed.