NuSTAR

NuSTAR (Nuclear Spectroscopic Telescope Array) is a NASA Small Explorer Program (SMEX) space-based X-ray telescope launched in 2012 aiming at a 2-year (minimum) mission to survey supermassive black holes. It remains active in 2023.

NuSTAR is a Wolter telescope, a telescope focusing the X-rays with grazing incidence optics, i.e., reflecting only at small angles from the reflecting surface, which gives a much better X-ray signal-to-noise ratio. This contributes to its ability to sense higher energy X-rays than previous missions. It has a 10-meter focal length, using a 10-meter mast that unfolded with deployment.