NuSTAR, or Nuclear Spectroscopic Telescope Array, is a space-based X-ray telescope launched in 2012 and operated by the California Institute of Technology in collaboration with NASA and other international partners. NuSTAR has the unique ability to focus high-energy X-rays with very high resolution, allowing it to study some of the most extreme phenomena in the universe, such as black holes, supernovae, and neutron stars. Its instruments consist of telescopes sensitive to X-rays with energies ranging from 3 to 79 keV, making it one of the most sensitive X-ray telescopes ever built.