First operation of Transition-Edge Sensors in space with the Micro-X sounding rocket

TL;DR

The Micro-X sounding rocket's first space flight successfully demonstrated the operation of Transition-Edge Sensors and SQUID readouts in space, highlighting performance and necessary upgrades for future missions despite limited science data due to pointing errors.

Contribution

This paper reports the first space flight of Transition-Edge Sensors with SQUID readouts, including performance assessment and upgrades for future reflight.

Findings

Detectors observed X-rays from calibration source in space

Magnetic susceptibility limited detector livetime

Flight performance matched ground tests

Abstract

With its first flight in 2018, Micro-X became the first program to fly Transition-Edge Sensors and their SQUID readouts in space. The science goal was a high-resolution, spatially resolved X-ray spectrum of the Cassiopeia A Supernova Remnant. While a rocket pointing error led to no time on target, the data was used to demonstrate the flight performance of the instrument. The detectors observed X-rays from the on-board calibration source, but a susceptibility to external magnetic fields limited their livetime. Accounting for this, no change was observed in detector response between ground operation and flight operation. This paper provides an overview of the first flight performance and focuses on the upgrades made in preparation for reflight. The largest changes have been upgrading the SQUIDs to mitigate magnetic susceptibility, synchronizing the clocks on the digital electronics to minimize beat frequencies, and replacing the mounts between the cryostat and the rocket skin to improve mechanical integrity. As the first flight performance was consistent with performance on the ground, reaching the instrument goals in the laboratory is considered a strong predictor of future flight performance.