In order to trace the evolution of dust past the classical T Tauri stage, c2d will conduct a photometric MIPS/IRAC survey of a large sample of weak-line T Tauri stars associated with star-forming clouds (ages 1-10 Myr). These measurements complement a larger goal of mapping several nearby (d &le 300 pc) star-forming clouds, such as the Perseus cloud imaged below. Targeted wTTs were selected on the basis of chromospheric activity indicated by X-ray brightness (e.g., Alcala et al. 2000) and optical emission lines, as well as proximity to the clouds and relatively low backgrounds. Since the inventory of known wTTs is contaminated by foreground stars of age 20 -- 100 Myr (Briceno et al. 1997, Favata et al. 1997), we are using lithium spectroscopy to clean the sample.

Several complications are expected to arise with respect to a straight-forward evolutionary interpretion of our SIRTF measurements. Multiple factors may affect disk size, mass, and evolution. In order to isolate age-dependent effects, we need to find any and all correlations between these factors and properties of the disk population. Our chief question will be: Is reduced disk emission the result of evolution or of initial conditions? To address this question, we require diagnostics of any and all factors which could affect disk formation and subsequent development. Optical spectroscopy provides a window onto stellar properties which may play a considerable role. These include stellar age, accretion state, multiplicity, stellar rotation, and association membership (via radial velocity).

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