The Rockets for Extended-source X-ray Spectroscopy (tREXS) is a suborbital rocket program that uses a wide-field grating spectrograph to obtain spectroscopic data on extended, soft-X-ray sources. The multi-channel tREXS spectrograph uses passive, mechanical focusing optics and stacks of reflection gratings to achieve a spectral resolution of R ≈ 50 from ≈15 – 40 Å over a >10 deg2 field of view. The dispersed spectra are read out by an array of 11 X-ray CMOS detectors that form a 97-megapixel focal-plane camera. tREXS was launched for the first time in September, 2022 to observe the Cygnus Loop supernova remnant. Though a failure in the rail pumping system led to a non-detection of emission from the Cygnus Loop during the flight, the rest of the instrument performed nominally and was recovered successfully. We present here an update on the instrument, results from the first flight, and a discussion of the future outlook.
Filter stacks in microcalorimeters (such as those being designed for the Athena X-IFU) must protect the detector from photon shot noise and thermal radiation, while being transparent to X-rays, being able to survive the mechanical loads from launch vibrations, survive a differential pressure during pumping, and be able to be maintained at a constant temperature with a small power draw. This research looks at the benefits of using SiC for the grid material compared to the steel/Au or silicon grids that are more traditionally used. Due to its material properties, SiC offers lower membrane stress and improved thermal conductance than the steel/Au counterpart allowing for smaller power draw to maintain filter temperature for contamination control. SiC also offers an increase in strength compared to Si grids with the SiC grids having been shown to be 5 times stronger over small apertures (10 mm). In the study, SiC grids have been developed, burst tested with a differential pressure, and vibration tested with vibration loads up to the NASA GEVS Qualification standard of 14.1 g rms. Optical inspection of the grids before and after vibration is used to show if the meshes can withstand standard launch vibration loads
This conference presentation was prepared for the conference on Space Telescopes and Instrumentation 2022: Ultraviolet to Gamma Ray, part of SPIE Astronomical Telescopes + Instrumentation, 2022.
The focal-plane camera on the Rockets for Extended-source X-ray Spectroscopy (tREXS) is a large-area detector array that takes advantage of the large-format, 3-side-buttable design of the Teledyne e2v Vega-CIS113 CMOS sensor. This paper discusses the initial design of the focal plane camera, results from testing that identified read noise performance issues, mechanical and electrical challenges of this initial design, and supply chain problems. The changes to the focal plane camera that were made due to these challenges are then presented, along with the final flight camera that has been designed to optimize noise performance and be able to be built within the schedule constraints of the tREXS mission.
The Rockets for Extended-source X-ray Spectroscopy (tREXS) are a funded series of sounding rocket instruments to detect diffuse soft X-ray emission from astrophysical sources. The first launch of tREXS is scheduled for Q4 2021, with a goal to observe the Cygnus Loop supernova remnant. tREXS house a four-channel grating spectrometer that uses passive, mechanical focusers, arrays of reflection gratings, and an extended focal plane based around Teledyne CIS 113 CMOS sensors. We present here an update on the instrument design, build, and calibrations in advance of the launch later this year.
The Rockets for Extended-source X-ray Spectroscopy (tREXS) are a series of NASA funded suborbital rockets that will make large field-of-view observations of the diffuse soft X-ray emission from the Cygnus Loop and Vela supernova remnants. The tREXS focal plane camera is made up of an array of 11 Vega-CIS113 CMOS detectors, with a 12th as the zero-order detector. To optimize the performance of the camera, a test setup was developed where a single CMOS detector can be characterized to determine which settings have the highest impact on detector performance characteristics such as readout noise. This paper will discuss this test setup, the initial testing that has occurred using an engineering grade detector, and the initial results on how changing bias potentials and pixel timings impact the readout noise. Improvements that will be made to the final focal plane camera electronics based on the findings in the initial testing will also be discussed.
The Rocket for Extended-Source X-ray Spectroscopy (tREXS) is a suborbital rocket payload that is designed to obtain the most highly resolved soft X-ray emission spectrum from the Cygnus Loop to date. This research will discuss the development and implementation of a guidance system that will replace the traditional pointing mechanism for a sub-orbital payload. Normally the pointing requirement for a sub-orbital flight is achieved using a NSROC altitude control system, which uses an ST5000 star tracker co-aligned with the X-ray optic. In tREXS design there is not space to use this star tracker; therefore, a design has been made that utilizes a side looking ST5000 to acquire the target field and an aspect camera for fine pointing. The aspect camera will stream frames of the target star field, that will be processed by the guidance algorithm. The algorithm will relay where to position the payload to target the Cygnus Loop.
HaloSat is a CubeSat-class microsatellite sensitive in the 0.4 to 7.0 keV energy band and designed to survey the entire sky in search of soft x-ray emissions from highly ionized oxygen residing in the halo of the Milky Way galaxy. Those observations will help constrain the mass and spatial distribution of the Milky Way halo and help us understand if hot galactic halos constitute a significant contribution to the overall cosmological baryon budget. We describe the science instrument calibration products, including channel-to-energy transformation, instrument energy resolution and instrument response, and the on-ground efforts that led to their creation. We also describe the alignment process used to obtain the field of view information for the HaloSat science instrument.
We have fabricated a blazed x-ray reflection grating with a period of 160 nm using thermally activated selective topography equilibration (TASTE) and electron-beam (ebeam) physical vapor evaporation. TASTE makes use of grayscale ebeam lithography to create three-dimensional (3-D) structures in resist, which can then be thermally reflown into a desired profile. A blazed grating profile can be fabricated by selectively reflowing a periodic staircase structure into a wedge. This was done for the first time at a grating period of 160 nm, 2.5 times smaller than previous x-ray gratings fabricated using TASTE. The grating was patterned over a 10 mm by 60 mm area in a 147-nm-thick layer of poly(methyl methacrylate) resist and coated with 5 nm of chromium and 15 nm of gold using ebeam evaporation. The diffraction efficiency of the grating was measured using beamline 6.3.2 at Lawrence Berkeley National Laboratory’s Advanced Light Source. The results show a total absolute diffraction efficiency ≳40 % at lower energies, with maximum single-order diffraction efficiency ranging from 20% to 40%. The total diffraction efficiency was ≳30 % across the measured bandpass of 180 to 1300 eV.
HaloSat is the first mission funded by NASA’s Astrophysics Division to use the CubeSat platform. Using three co-aligned silicon drift detectors, the HaloSat observatory measures soft (0.4 to 7 keV) x-ray emission from sources of diffuse emission such as the hot, gaseous halo of the Milky Way. We describe the design and construction of the science payload on HaloSat and the reasoning behind many of the choices. As a direct result of the design choices and adherence to best practices during construction, the HaloSat science payload continues to perform well after more than one year on-orbit.
We have fabricated a blazed X-ray reflection grating with a period of 160 nm using thermally activated selective topography equilibration (TASTE). The grating was tested for diffraction efficiency using the soft X-ray reflectometer at Lawrence Berkeley National Laboratory's Advanced Light Source. Preliminary results show total absolute diffraction efficiency ≥ 40% at lower energies, with maximum single order diffraction efficiency ranging from 20-40%. Total diffraction efficiency was ≥ 30% across the entire measured band pass of 180 eV to 1300 eV.
The Rockets for Extended-source X-ray Spectroscopy (tREXS) are a series of suborbital rocket payloads being developed at The Pennsylvania State University. The tREXS science instrument is a soft X-ray grating spectrometer that will provide a large field-of-view and unmatched spectral resolving power for extended sources. Each instrument channel consists of a passive, mechanical focusing optic and an array of reflection gratings. The focal plane consists of an array of CIS113 CMOS sensors. tREXS I is currently in the design phase and is being developed for a launch in 2021 to observe diffuse soft X-ray emission from the Cygnus Loop supernova remnant. An analysis of instrument optics, gratings, and focal plane camera is discussed.
Astronomical X-ray diffraction gratings are a key technology under development for current and future NASA missions. X-ray reflection gratings, developed at Penn State University, have recently demonstrated both leading diffraction efficiency and high spectral resolving power. However, recent results are the result of different fabrication techniques and a single technique has not yet been developed to yield a grating that satisfies both the diffraction efficiency and resolving power required by future missions. Here we seek to leverage exiting electron-beam lithographic techniques to produce a grating with groove groove pattern capable of high resolving power. We then introduce new ion-milling techniques to create custom groove profiles capable of high diffraction efficiency. The goal is to produce a radial groove pattern with precisely blazed facets that are customizable based on ion mill input parameters. The process should be insensitive to groove density (ranging from ~150 nm to 400+ nm), facet size, and desired facet angle. Initial efforts in this study have concentrated on constraining various parameters in ion milling to fully characterize the effect of each parameter on the grating groove profile. We present here initial results and discuss experimental verification and future work.
The Polarimeter for Relativistic Astrophysical X-ray Sources (PRAXyS) is one of three Small Explorer (SMEX)
missions selected by NASA for Phase A study. The PRAXyS observatory carries an X-ray Polarimeter Instrument (XPI)
capable of measuring the linear polarization from a variety of high energy sources, including black holes, neutron stars,
and supernova remnants. The XPI is comprised of two identical mirror-Time Projection Chamber (TPC) polarimeter
telescopes with a system effective area of 124 cm2 at 3 keV, capable of photon limited observations for sources as faint
as 1 mCrab. The XPI is built with well-established technologies. This paper will describe the performance of the XPI
flight mirror with the engineering test unit polarimeter.
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