We will exploit the sensitivity of SIRTF to carry out spectrophotometric observations of solar-type stars aimed at (1) denning the timescales over which terrestrial and gas giant planets are built, from measurements diagnostic of dust/gas mass and radial distribution; and (2) establishing the diversity of planetary architectures and the frequency of planetesimal collisions as a function of time from high precision spectral energy distributions (and model calculations) capable of diagnosing the radial distribution of dust and the dynamical imprints of embedded giant planets. Together, these observations will provide an astronomical context for understanding whether our solar system - and its habitable planet - is a common or a rare circumstance. Achieving our science goals requires measuring precise spectral energy distributions for a statistically robust sample capable of revealing evolutionary trends arid the diversity of system outcomes. Our targets have been selected from two carefully assembled databases of solar-like stars: (1) a sample located within 50 pc of the Sun (150 out of nearly 5000 candidates) spanning an age range from 100-3000 Myr for which a rich set of ancillary measurements (e.g. metallicity, stellar activity, kinematics) are available; arid (2) a selection located between 15 and 180 pc and spanning ages from 3 to 100 Myr (150 out of ～1000 candidates). For stars at these distances SIRTF is capable of detecting stellar photospheres with SNR > 30 at λ ≤ 24μm for our entire sample, as well as achieving SNR > 5 at the photospheric limit for over 50% of our sample at λ = 70μm. Thus we will providing a complete census of stars with excess emission down to the level produced by the dust in our present-day solar system. Our calibration plan links observation of these 300 targets to a grid of carefully selected calibration standards, and defines an observing strategy that will provide frequent internal arid external checks. SIRTF observations obtained as part of this program will provide a rich Legacy for follow-up observations over the next decade and beyond.
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