https://phys.org/news/2018-07-nasa-x-ray-telescope-rocket-star.html

Launched from the U.S. Army's White Sands Missile Range in New Mexico, Micro-X soared to an altitude of 100 miles (160 kilometers)—required to detect X-rays that are absorbed by Earth's atmosphere—and observed the remnant for the next five minutes. At its pinnacle Micro-X reached an altitude of 167 miles (270 kilometers).

The mission incorporates the first array of transition-edge sensor X-ray microcalorimeters to fly into space. These sensors act as highly sensitive thermometers and make ideal detectors for an X-ray telescope.