Japanese activities of far-infrared astronomical spectroscopy with balloon-borne telescopes Original Research Article

We review Japanese activities of balloon-borne far-infrared astronomical spectroscopic observations. Most of our experiments have focused on spectroscopic mapping observations of the far-infrared [C II] line at 158 μm, which is the dominant coolant of general interstellar gas and is a key tracer of interstellar energetics. We made two types of observations. One is large-scale survey observations with a dedicated system which has an offset low-emissivity telescope. The other is detailed observations of individual sources with a multi-purpose 50 cm telescope. In addition to the conventional spatial chopping method, we used spectral modulation techniques with a Fabry-Perot spectrometer in these experiments to make efficient mappings of spatially extended sources. Major scientific results of these experiments are briefly reviewed. New collaborative project with TIFR, India started in 1998, to make high-resolution spectroscopic mapping observations of star-forming regions with the TIFR 1 m telescope and the Japanese Fabry-Perot spectrometer.