FIGURE 4.1a (top) Photometric sensitivity of three proposed facilities, SIRTF, SOFIA, and the infrared-optimized (IRO) 8-m telescope (solid squares) for broadband observations. For reference the figure also gives the sensitivity of the KAO, the 3-m IRTF (open squares), and the IRAS survey (solid triangles). Technical assumptions underlying these curves can be found in the report of the Infrared Astronomy Panel in the Working Papers (NRC, 1991).

FIGURE 4.1b (bottom) SIRTF's sensitivity (solid lines) for photometry [resolution (R) = 2] and spectroscopy [resolution (R) = 100] compared with the predicted brightnesses of representative extragalactic objects scaled to a common redshift of 5, when the universe was only one-sixth its present size. SIRTF could detect luminous galaxies, quasars, and protogalaxies in the early universe.