The IRTS (Infrared Telescope in Space) was a highly-successful 15-cm-diameter orbiting infrared telescope developed by Japan's ISAS (Institute of Space and Astronautical Science), launched aboard Japan's SFU (Space Flyer Unit), and retrieved by the Space Shuttle Endeavour on mission STS-72 in December 1995. Attached to the telescope were four instruments: a near-infrared spectrometer (NIRS), a mid-infrared spectrometer (MIRS), a far-infrared line mapper (FILM), and a far-infrared photometer (FIRP). MIRS and FIRP were built in collaboration with American researchers. IRTS operated from 30 March 1995 to 26 April 1995, when its supply of cryogenic coolant ran out.