Measurements in interplanetary space and in the Martian upper atmosphere with a hydrogen absorption-cell spectrophotometer for Lalpha -radiation onboard Mars 4 - 7 spaceprobes.

Direct temperature measurements of neutral interstellar hydrogen near the sun and in the upper atmosphere of Mars were obtained with the hydrogen absorption-cell ultraviolet spectrophotometers on board the Mars 4-7 space probes. The spectrophotometers were designed to measure the intensity and spectral characteristics of emissions in the Lyman-alpha lines of atomic hydrogen and atomic deuterium. Interstellar wind temperatures of about 12,000 K and upper Martian atmosphere temperatures of 340 plus or minus 30 K are reported.