Advanced Concepts Studies

Edison Telescope

The Edison Telescope is a long-lived, international infrared space observatory, possessing a 1.7 m mirror cooled via radiation to 20 K and operating at the diffraction limit for l _ 5 mm. The observatory will be equipped with imaging and spectroscopic instruments operating over the wavelength range ~ 2 mm to 100+ mm. High sensitivity, high angular resolution, and long life due to lack of cryogens will allow Edison to undertake a comprehensive research program impossible with any other existing or proposed facility, including

• the chemical and physical structure of Solar System objects;

• planetary material around normal stars in the Milky Way and Local Group;

• age, mass, and chemical composition of brown dwarfs and other sub-stellar objects;

• fundamental processes of stellar death, including the enrichment of the interstellar medium via novae and supernovae, observable throughout the local Universe;

• the physical condition of the interstellar medium, including its chemical composition, energy balance, and magnetic field structure;

• the structure, composition, energetics, dynamics, and evolution of galaxies of all types, from nearby abundant star forming dwarfs to energetic "ultraluminous" interacting systems and normal spirals at the edge of the observable Universe.

The innovative use of radiative cooling allows a much larger telescope for a given overall spacecraft size, and avoids much complex and expensive engineering. For l _ 50 mm all proposed space observatories are limited by the celestial thermal background, which gives the advantage to Edison's large aperture. For broadband observations at _ 70 mm, sensitivity is ultimately dominated by the crowding of large numbers of sources. Under these conditions, a large cool (radiative) telescope will reach fainter flux levels than can a smaller cold (cryogenic) telescope. Equipped with modern array detectors, Edison will be by far the most sensitive infrared observatory in orbit or on the ground, either in existence or proposed.

Edison will be a modestly-sized spacecraft: 5.3 m x 2.4 m and weighing about 2360 kg, approximately the same overall size as ESA's Infrared Space Observatory (ISO), which possesses a 0.6 m aperture. The baseline Edison telescope will be launched by an Atlas IIAS, Ariane 4/5, or Proton vehicle into a "halo" orbit around the second Earth-Sun Lagrangian point (L2), about 1.5 million km anti-sunward from the Earth. Cooled primarily via radiation, the optical system will equilibrate at about 20 K. The detectors will be further cooled by long-life mechanical refrigerators now in an advanced stage of development by ESA. The baseline design uses a service module similar to that of the SOHO mission.