EDISON is a large-aperture telescope under study for the second generation of infrared space observatories, whether in orbit or on the moon. The optics equilibrate via radiative cooling to temperatures between 40 and 80 K, depending upon, for example, telescope structure and location. At these temperatures, telescope emission is below that of the astronomical background at all wavelengths shortward of 20-40 μm. The detector components can be cooled via mechanical refrigerators now in an advanced stage of development. A mixture of radiative and mechanical cooling means that there is no natural limit to EDISON’s lifetime. In addition, the upper stage rocket fairing can be almost filled with light-collecting optics and alternative low-emissivity optical designs, such as off-axis systems, can be easily engineered. We are presently evaluating a design for a 2.5 m observatory to be launched in collaboration with European astronomers as part of the NASA Explorer program. In this presentation, we describe possible spectroscopic and spectrophotometric studies of very faint infrared sources that will require large-aperture space telescopes working at the celestial background limit.