The optics have an overall length of 450 mm (1.5 feet), a maximum radius of 191 mm (7.5 inches) and a focal length of 10 m (33 feet). NuSTAR flies two of these units and each of them weight 38 kg (84 lbs).

Each focusing optic consists of 133 concentric shells. The shells are coated with alternating atomically thin layers of a high-density and low-density special material which enables reflectivity up to 79 keV. To achieve enhanced reflectivity, a high density contrast between the two materials is needed, and common high density materials are Tungsten (W) and Platinum (Pt), while common materials for the low density layers are Silicon (Si), Carbon (C), and Silicon Carbide (SiC).

The optics follow the Wolter Type 1 Design and has a total weight of 350 kg.

NuSTAR'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.

In 2014, NASA's Nuclear Spectroscopic Telescope Array, or NuSTAR, and Swift space telescopes witnessed an X-flare from the supermassive black hole in a distant galaxy called Markarian 335. The observations allowed astronomers to link a shifting corona to an X-ray flare for the first time.

NuSTAR typically stares deeper into the cosmos to observe X-rays from supernovas, black holes and other extreme objects. But it can also look safely at the sun and capture images of its high-energy X-rays with more sensitivity than before. Scientists plan to continue to study the sun with NuSTAR to learn more about microflares, as well as hypothesized nanoflares, which are even smaller.