First flight performance of the Micro-X microcalorimeter X-ray sounding rocket

The flight of the Micro-X sounding rocket on July 22, 2018, marked the first operation of transition-edge sensors and their superconducting quantum interference device readouts in space. The instrument combines the microcalorimeter array with an imaging mirror to take high-resolution spectra from extended X-ray sources. The first flight target was the Cassiopeia A supernova remnant. Although a rocket pointing malfunction led to no time on-target, data from the flight were used to evaluate the performance of the instrument and demonstrate the flight viability of the payload. The instrument successfully achieved a stable cryogenic environment, executed all flight operations, and observed X-rays from the on-board calibration source. The flight environment did not significantly affect the performance of the detectors compared with ground operation. The flight provided an invaluable test of the impact of external magnetic fields and the instrument configuration on detector performance. This flight provides a milestone in the flight readiness of these detector and readout technologies, both of which have been selected for future X-ray observatories.