  The flight of the Micro-X sounding rocket on July 22, 2018 marked the first
operation of Transition-Edge Sensors and their SQUID 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. While a rocket pointing malfunction led
to no time on-target, data from the flight was 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 to 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.
