  Micro-X is a sounding rocket-borne instrument that uses a microcalorimeter
array to perform high-resolution X-ray spectroscopy. This instrument flew for
the first time on July 22nd, 2018 from the White Sands Missile Range, USA. This
flight marks the first successful operation of a Transition-Edge Sensor array
and its time division multiplexing read-out system in space. This launch was
dedicated to the observation of the supernova remnant Cassiopeia A. A failure
in the attitude control system prevented the rocket from pointing and led to no
time on target. The on-board calibration source provided X-rays in flight, and
it is used to compare detector performance during pre-flight integration,
flight, and after the successful post-flight recovery. This calibration data
demonstrates the capabilities of the detector in a space environment as well as
its potential for future flights.
