Infrared Observations of the Outer Solar Corona

Observations of the outer solar corona at wavelength 2.2 ,~ have been carried out in two experiments: during the period of totality of the solar eclipse of November 12, 1966, with the use of a ground-based telescope, and during a stratospheric balloon ifight on January 9, 1967, by employing a coronagraph. The experiments are discussed, and the coronal radiance is presented over the range 3-10 Ro. The presence of four features is attributed to thermal emission of interplanetary dust. Scans obtained from the balloon experiment over a range of position angles show isophotes peaked away from the ecliptic at a position which closely coincides with the invariable plane. Attempts to assess the origin of the continuum radiance are presented and lead to calculations of a scattered infrared F- coronal component and a thermal component based upon large-particle cross-sections