Probing the Substellar Regime with SIRTF

One of the main scientific drivers of the Space Infrared Telescope Facility (SIRTF) is the search for brown dwarfs and extrasolar superplanets. We present new calculations of the spectra of substellar objects and a prediction of their colors in the SIRTF passbands. We discuss observational strategies for identification of very low mass objects as free-floaters in the solar vicinity and provide estimates of their densities as a function of sensitivity and the mass function.