The future is BLISS – sensitive far-IR spectroscopy on SPICA and SAFIR

Half the energy produced since decoupling emerges in the far-IR, hence a complete understanding of the history of stellar nucleosynthesis and galaxy evolution requires a systematic study of dust-enshrouded energy release at all epochs. Sensitive far-IR spectroscopy is the natural tool for this, and we present the first opportunity for cosmological far-IR spectroscopy with new cryogenic telescopes and instruments. We are studying a US-built spectrograph BLISS for the Japanese SPICA mission to launch in 2013, and NASA’s SAFIR mission, envisioned for 2025. With sensitive detectors and the very low backgrounds provided by the cold telescope, we anticipate 5–8 orders of magnitude speed improvement relative to preceeding platforms, enabling measurements throughout the epoch of peak activity in galaxies, to z ∼ 5.