Building on the enormous success of its recent space and airborne infrared observatories (IRAS, COBE and the KAO, plus a piece of ISO), NASA plans three new infrared missions in the coming decade: the Wide Field Infrared Explorer (WIRE), the Space Infrared Telescope Facility (SIRTF) and the Sub-Orbital Facility for Infrared Astronomy (SOFIA). The usefulness of the SDSS for these and other new missions in terms of source identification, wavelength coverage, and the optical flux densities of guide stars is obvious; this short discussion will concentrate on the survey modes of these new missions. WIRE is a survey instrument working at 12 and 25 µm , while SIRTF (Werner and Simmons 1995) and SOFIA will operate in pointed, observatory mode, although the former plans to carry out several deep surveys between about 25 and 100 µm in small regions of the sky.
WIRE plans to survey about 200 square degrees of the sky with fields at both low and high galactic latitudes to a sensitivity about 500 times that of the IRAS Faint Source Catalogue. SIRTF includes among its scientific plans deep surveys of small regions of the sky with low cirrus emission at wavelengths between about 20 µm and 100 µm . The primary scientific topic to be tackled by WIRE is the ultraluminous starburst galaxy phenomenon, with investigations focusing on the number density of these galaxies (WIRE should find roughly 105of these objects), their redshift evolution, and the starburst galaxy/quasar connection.
Starburst galaxies are so dusty, chaotic and hot that they are bright at 12 µm and 25 µm , in contrast to more normal galaxies, and can be identified by their 12/25 µm colors. The sensitivity of the deepest of the proposed SIRTF surveys to these objects is comparable to that of WIRE; and so, as it turns out, is the SDSS Northern survey (with the SDSS Southern survey going even deeper). The comparison of optical and IR data will greatly aid the identification of galaxies in the WIRE data; the SDSS will provide images; and it may be possible to estimate quite decent photometric redshifts from a comparison of the optical and infrared data. The brightest thousand or so starburst galaxies found by WIRE will be included in the SDSS spectroscopic survey, so that we can get a good estimate of the luminosity function and the clustering of these rare galaxies. Comparison of the WIRE and SDSS data will allow us to estimate the number of starburst galaxies which are so dusty that they are undetectable at visible wavelengths. All in all, the comparison of SDSS data with the results of the WIRE and SIRTF surveys is likely to provide a lot of exciting information about starburst galaxies and AGNs, and should make possible the discovery of new classes of objects.
Werner, M.W., & Simmons, L.L. 1995, Space Sci. Rev., 74, 125.