Journal of The Korean Astronomical Society

We present the results of an rocket-borne observation of far-infrared [CII] line at 157.7¯m from the diffuse interstellar medium in the Ursa Major. We also introduce a part of results on the [CII] emission recently obtained by the IRTS, a liquid-helium cooled 15cm telescope onboard the Space Flyer Unit. From the rocket-borne observation we obtained the cooling rate of the diffuse HI gas due to the [CII] line emission, which is 1:3 \Sigma 0:2 \Theta 10 \Gamma26 ergss \Gamma1 H \Gamma1 atom . We also observed appreciable [CII] emission from the molecular clouds, with average CII/CO intensity ratio of 420. The IRTS observation provided the [CII] line emission distribution over large area of the sky along great circles crossing the Galactic plane at l = 50 ffi and l = 230 ffi . We found two components in their intensity distributions, one concentrates on the Galactic plane and the another extends over at least 20 ffi in Galactic latitude. We ascribe one component to the emissio..