  Current observational data is consistent with the universe being slightly
closed. We investigate families of singular and non-singular closed instantons
that could describe the beginning of a closed inflationary universe. We
calculate the scalar and tensor perturbations that would be generated from
singular instantons and compute the corresponding CMB power spectrum in a
universe with cosmological parameters like our own. We investigate spatially
homogeneous modes of the instantons, finding unstable modes which render the
instantons sub-dominant contributions in the path integral. We show that a
suitable condition may be imposed on singular closed instantons, constraining
their instabilities. With this constraint these instantons can provide a
suitable model of the early universe, and predict CMB power spectra in close
agreement with the predictions of slow-roll inflation.
