Spitzer Space Telescope - Directors Discretionary Time Proposal #26 First Look Survey -- Extragalactic Component Principal Investigator: Tom Soifer Institution: Spitzer Science Center Science Category: high-z galaxies (z>0.5) Observing Modes: IracMap MipsScan Hours Approved: 62.5 Abstract: The SIRTF First Look Survey extragalactic component is designed to: 1. detect enough extragalactic sources at unexplored sensitivity levels to generate a representative sample and reduce the uncertainties in the source counts, 2. characterize the dominant source populations with both MIPS and IRAC data from SIRTF plus ancillary surveys at optical, near-infrared, and radio wavelengths, and, 3. explore the cirrus foreground at moderately high abs(b), and its effect on point-source detectability. This component is comprised of MIPS and IRAC surveys of four square degrees in the SIRTF northern continuous viewing zone (CVZ) and 1 square degree in the Elais N1 field. A verification survey covering a small region of the CVZ and Elais fields is also included.