The Single Aperture Far-Infrared observatory (SAFIR) is a large cryogenic space telescope scheduled for launch around 2015 to 2020. "Single Aperture" refers to the telescope's single primary mirror, distinguishing it from multi-mirror interferometry missions.
SAFIR will study the earliest phases of forming galaxies, stars, and planetary systems at wavelengths where these objects are brightest and which contain a wealth of unique information: from 20 microns to one millimeter. Most of this portion of the electromagnetic spectrum is not accessible from the ground because it is absorbed by moisture in Earth's atmosphere.
SAFIR's primary mirror is expected to be eight to ten meters in diameter, quite large for a space-based telescope. For comparison, SAFIR's predecessor, the Spitzer Space Telescope (Spitzer), launched in 2003, has a primary mirror only 0.85 meters in diameter.