Takao Nakagawa

Far-infrared spectroscopic observations have been made using a 50cm balloon-borne infrared telescope, a superfluid helium cooled Fabry-Perot spectrometer, and a frequency switching method, which is a newly developped observational technique. Remarkable two-dimensional [CII] line intensity maps constructed from the data show us that the [CII] 158μm line is strongly emitted not only from the photodissociation regions but also from their surrounding regions and from general region of the Galactic Plane. This fact indicates singly ionized carbon ions and carbon ioinizing UV photons should be abundantly distributed in interstellar clouds of the Galactic Plane. Since the energy emitted in form of the [CII] 158μm line can reach up to 0.5% of the total energy output of the clouds, the [CII] line must be one of the dominant coolants of the interstellar cloud.

Far-infrared H_2O emission spectra of the upper atmosphere have been obtained during a balloon flight in Alice Springs, Australia. Analyses show that the emission features of the telluric H_2O are fitted by a model atmosphere of 245K in mean temperature and of 1.7×10^<18>cm^<-2> in H_2O column density. We have also made an assessment for the telluric H_2O absorption via this model, thus anabling a correction of the observed astronmical spectra.