NuSTAR (Nuclear Spectroscopic Telescope Array, also named Explorer 93 and SMEX-11) is a NASA space-based X-ray telescope that uses a conical approximation to a Wolter telescope to focus high energy X-rays from astrophysical sources, especially for nuclear spectroscopy, and operates in the range of 3 to 79 keV.
NuSTAR is the eleventh mission of NASA's Small Explorer (SMEX-11) satellite program and the first space-based direct-imaging X-ray telescope at energies beyond those of the Chandra X-ray Observatory and XMM-Newton. It was successfully launched on 13 June 2012, having previously been delayed from 21 March 2012 due to software issues with the launch vehicle.
The mission's primary scientific goals are to conduct a deep survey for black holes a billion times more massive than the Sun, to investigate how particles are accelerated to very high energy in active galaxies, and to understand how the elements are created in the explosions of massive stars by imaging supernova remnants.
Having completed a two-year primary mission, NuSTAR is in its twelfth year of operation.