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"The Long-Awaited Dawn of Space X-ray Calorimetry"
THE JOHN C. LINDSAY MEMORIAL LECTURE
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Imaging spectrometers are essential tools in many fields and wavebands. These instruments, also known as hyperspectral imagers and integral field units, acquire spatially resolved spectra across an imaging focal plane. High resolution (both spatial and spectral) imaging spectrometers are sought in all wavebands but are slightly more tractable to build in the X-ray band due to the ability to obtain high energy resolution with non-dispersive X-ray spectrometers that operate at low temperatures.
In astrophysics, X-rays are strongly radiated by cosmic gas heated to more than 1 MK, such as is found in the remnants of supernovae, in the gravitational potential of clusters of galaxies, and accreting onto black holes and neutron stars. The characteristic emission lines of the most abundant non-primordial elements lie in the X-ray regime, and high-resolution X-ray spectroscopy can tell us about the composition of the matter, its temperature, and its kinematics.
The quest to perform imagining spectroscopy on extended cosmic X-ray sources, with energy resolution high enough to separate and characterize diagnostic spectral features, began four decades ago, with the invention at Goddard of the first X-ray microcalorimeters. A microcalorimeter is a device operated at very low temperatures (<0.1 K) that makes precise measurements of small amounts of energy by measuring the temperature changes they produce when deposited in an absorber with low heat capacity. In our presentation, we will review the operating principles of microcalorimeters, their configurability to different requirements, and a bit of their history before dwelling a bit on the technology, performance, and discoveries of XRISM's Resolve spectrometer, which has been operating in orbit since October 2023. We will conclude by looking towards an exciting future of large scale, high-resolution X-ray imaging spectrometers: NewAthena's X-IFU and beyond.
About the Speakers
Dr. Caroline Kilbourne is a physicist at Goddard Space Flight Center, where she's been developing detectors for high-resolution X-ray spectroscopy since 1992. Her responsibilities have ranged from leading advanced detector development at the sensor level to developing and building robust, space-worthy instrumentation. In 2022 she was awarded a NASA Distinguished Service Medal for her mission-enabling developments. She is currently, along with her colleague Dr. F. Scott Porter, one of the instrument scientists for the Resolve spectrometer of the operating XRISM observatory.
Dr. F. Scott Porter has been an Astrophysicist at Goddard Space Flight Center for almost 30 years. He has a strong interest in diffuse X-ray emitting objects, laboratory astrophysics, and X-ray instrumentation. He has built X-ray instruments for many sub-orbital and orbital platforms often with his colleague Dr. Caroline Kilbourne, including the cryogenic X-ray instrument on the recent XRISM observatory. He is also deeply involved in a number of upcoming missions including NewAthena, SMILE, LEXI, LiteBird, and the LXT sounding rocket payload.