Chandra X-ray Observatory

The Chandra X-ray Observatory (CXO) is a space telescope launched by NASA on July 23, 1999. 
Chandra is sensitive to X-ray sources 100 times fainter than any previous X-ray telescope. This is done by the high angular resolution of its mirrors. Since the Earth's atmosphere absorbs the vast majority of X-rays, Earth-based telescopes cannot detect them. Space-based telescopes are needed to make these observations. Chandra is an Earth satellite in a 64-hour orbit, and its mission is ongoing as of 2021.
Chandra is one of the Great Observatories, with the Hubble Space Telescope, Compton Gamma Ray Observatory (1991–2000), and the Spitzer Space Telescope. The telescope is named after Subrahmanyan Chandrasekhar.