The Frontier in X‐ray Spectroscopy: NASA’s Constellation‐X Mission

This paper briefly describes the Constellation‐X mission, giving its basic performance parameters such as effective area and spectral resolution, describes some example science that may be conducted, and gives a general update on the mission, due for launch in 2016. Constellation‐X is one of the two flagship missions for the Beyond Einstein programand was designated as a high priority, second only to JWST, in the large space observatories category of the most recent National Academy decadal. Constellation‐X will present a great improvement in spectroscopic sensitivity, enabling studies at sensitivities more than 100 times greater than the best high‐resolution spectrometers observing in the 0.25–10 keV band during the current decade. The spectral resolution, R = E/ΔE, will range from 300 to 3000.