  Micro-X is an X-ray sounding rocket payload that had its first flight on July
22, 2018. The goals of the first flight were to operate a transition edge
sensor (TES) X-ray microcalorimeter array in space and take a high-resolution
spectrum of the Cassiopeia A supernova remnant. The first flight was considered
a partial success. The array and its time-division multiplexing readout system
were successfully operated in space, but due to a failure in the attitude
control system, no time on-target was acquired. A re-flight has been scheduled
for summer 2022. Since the first flight, modifications have been made to the
detector systems to improve noise and reduce the susceptibility to magnetic
fields. The three-stage SQUID circuit, NIST MUX06a, has been replaced by a
two-stage SQUID circuit, NIST MUX18b. The initial laboratory results for the
new detector system will be presented in this paper.
