Development of space-flight room-temperature electronics for the Line Emission Mapper Microcalorimeter Spectrometer

We are developing space-flight room-temperature readout electronics for the Line Emission Mapper (LEM) Microcalorimeter Spectrometer (LMS) of the LEM mission. The LEM mission is an x-ray probe mission designed to study the physics of galaxy formation. The LMS is optimized for low-energy (0.2 to 2 keV) x-ray emission from extremely diffuse gas. The detector is a hybrid transition-edge sensor (TES) microcalorimeter array with a 33′ outer array and a 7 ′ × 7 ′ inner subarray. The outer array consists of 12,736 square pixels on a square grid with a 290 μm pitch but in a close-packed hexagonal shape. The inner subarray consists of 784 TES sensors arranged in a square area in the center of the outer array with the same pixel pitch. The outer array uses a sensor with 2 × 2 thermal multiplexing known as “Hydra,” and the inner array consists of a single absorber per TES. The baselined readout technology for the 3968 TES sensors is time-division multiplexing (TDM), which divides the sensors into 69 columns × 60 rows. The components of the room temperature readout electronics are the three boxes of the warm front-end electronics (WFEE) and the six boxes of the digital electronics and event processor (DEEP). The WFEE is an interface between the cold electronics and the DEEP, and the DEEP generates signals for the TDM and processes x-ray events. We present the detailed designs of the WFEE and DEEP. We also show the estimated power, mass, and size of the WFEE and DEEP flight electronics. Finally, we describe the performance of the TRL-6 prototypes for the WFEE and DEEP electronics.