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The X-ray Integral Field Unit(X-IFU) of the Athena observatory, scheduled for launch in the mid2030's, will provide X-ray spectroscopy data with unprecedented spectral and spatial resolution. This will be achieved with a 2kilo-pixel array of transition-edge sensor (TES) microcalorimeters. The complete detection chain is under development by a large international collaboration. In order to perform an end-to-end demonstration of the X-IFU readout chain, a 50 mK test bench is being developed at IRAP in collaboration with CNES. The test bench uses a two-stage ADR cryostat from Entropy GmbH, a 1024-pixelarray, and will initially be operated using a warm electronics chain from NIST and NASA Goddard Space Flight Center. We describe the complete system being installed in the cryostat and the current results obtained with these electronics. We also review the status of the integration of the digital readout electronics (DRE)prototype into the demonstration chain and the plan for integrating and testing the complete X-IFU readout chain.

Future X-ray astrophysics experiments require multiplexed readout of high fill-factor, kilo-pixel arrays of transition-edge sensors (TESs), with very high spectral resolution over a broad range of energies. In this paper we report on a prototype kilo-pixel array of Mo/Au TESs readout with 8-column by 32-row time-division multiplexing (TDM). This system is being used to demonstrate the critical detector and readout technology for ESA’s Athena X-IFU, and when complete will be used in laboratory astrophysics experiments. Our array and TDM readout have demonstrated a combined full-width-at-half-maximum energy resolution, including >200 pixels, of:1.95 eV for Ti-Ka(4.5 keV), 1.97eV for Mn-Ka(5.9 keV), 2.16 eV for Co-Kα(6.9 keV),2.33 eV for Cu-Kα(8 keV), 3.26 eV for Br-Kα(11.9 keV). The 1 sigma statistical errorsare£0.01 eV for all spectra. These results meet the broad-band resolution requirements for X-IFU with margin.

The Micro-X sounding rocket flew for the first time on July 22, 2018, becoming the first program to fly Transition-Edge Sensors and multiplexing SQUID readout electronics in space. While a rocket pointing failure led to no time on-target, the success of the flight systems was demonstrated. The successful flight operation of the instrument puts the program in a position to modify the payload for indirect galactic dark matter searches. The payload modifications are motivated by the science requirements of this observation. Micro-X can achieve world-leading sensitivity in the keV regime with a single flight. Dark matter sensitivity projections have been updated to include recent observations and the expected sensitivity of Micro-X to these observed fluxes. If a signal is seen (as seen in the X-ray satellites), Micro-X can differentiate an atomic line from a dark matter signature.

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 readout 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 onboard calibration source provided X-rays in flight, and it is used to compare detector performance during preflight integration, flight, and after the successful post-flight recovery. This calibration data demonstrate the capabilities of the detector in a space environment as well as its potential for future flight.