The IRTS (Infrared Telescope in Space) was launched on March 18th UT by the H-II rocket as a part of the Space Flyer Unit (SFU), which is a re-usable free flyer designed as a multi-purpose common facility for scientific and engineering experiments. The IRTS, cooled by He II at 1.91K, had successfully completed the whole infrared astronomical observation mission for 37 days, and every detector for the observation in the whole infrared region worked quite satisfactorily. A tremendous amount of observation data was obtained which is now being analyzed. On January 27th, 1996, the SFU was retrieved by a US Space Shuttle. In this report, the flight data of the thermal performance of the cryogenic system is discussed and the development of the IRTS is also briefly described.
