Observations of the Universe in the Terahertz Range: From AKARI to SPICA

One of the biggest challenges for the current astrophysics research is to reveal the history of the evolution of the universe. To achieve the goal, sensitive observations in the Terahertz range are essential since significant fraction of the the total energy is emitted in the range. However, the atmosphere of the earth is opaque mostly in the range, and space telescopes are required for sensitive observations. We discuss examples of the Terahertz observations of the universe using space telescopes, focusing on Japan-related infrared astronomical satellites AKARI (launched in 2006) and SPICA (expected to be launched in the 2020s).