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"To take the next step in exploring this important part of the spectrum [30-300μm], the committee recommends the Single Aperture Far-Infrared Observatory (SAFIR)." - Astronomy and Astrophysics in the New Millennium, 2001 . In response to this recommendation, we have undertaken a study of the enabling technologies for a large single aperture far-infrared telescope such as SAFIR. A broad list of science investigations was produced and used to generate an explicit list of science requirements, from which top-level engineering requirements were derived. From these requirements, we developed a conceptual design for the SAFIR observatory based on NGST's current designs. A detailed analysis has been made of the changes and technologies necessary to produce SAFIR. Crucial technologies requiring innovation include lightweight deployable optics, cryogenic cooling of optical elements and instruments, and large arrays of sensitive detectors. Cryogen-free refrigeration technologies are necessary for SAFIR's long mission lifetime, and will have to provide significant (~100mW) cooling power at 4K to cool the mirrors while providing very low temperatures (~50mK) for detector arrays. The detector arrays require wide wavelength coverage, thousands of continuum elements, and compatibility with broadband and spectroscopic instruments.

Spartan Lite is a proposed series of very low-cost spacecraft missions which offer potential flight opportunities for pointed solar experiments. Early versions will be launched as Space Shuttle attached payloads with the capability of being released for free flight. They would not be recovered, allowing useful lifetimes of six months to one year. An expendable launch vehicle option will be added later. The spacecraft is 3-axis stabilized with a cylindrical instrument cavity 100 cm long and 36 cm in diameter. If approved, the program would provide multiple launch opportunities during the upcoming solar maximum. A conceptual instrument design for a solar pointed mission on Spartan Lite is shown and discussed. The Extreme-Ultraviolet Normal Incidence Spectrograph will observe the solar spectrum between 290 and 466 A with high spatial and spectral resolutions. The large bandpass is due to the compact design, fitting two optical systems into the instrument cavity, each observing a different, but overlapping, wavelength range.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.