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.
The Off-Plane Grating Rocket Experiment (OGRE) will flight-test high-precision X-ray technology in a three-component spectrometer comprised of a Wolter-I telescope, X-ray reflection gratings and electron-multiplying charge-coupled devices (EM-CCDs). OGRE will demonstrate cutting-edge X-ray mirrors known as monocrystalline silicon optics which are planned for use on several proposed X-ray Probe missions, and fly X-ray reflection gratings that after our recent characterization campaign, indicate high-precision spectral resolution. This X-ray technology serves as a great candidate for space-based X-ray astronomy as we move towards a Lynxlike flagship mission, and OGRE will be the first mission to test such gratings and optics in space. However, mono-crystalline silicon optics are still in development, while the gratings and electronics section of OGRE will be ready for a flight-test in the immediate future. In the interim, it is proposed that OGRE achieves a pathfinder flight which incorporates the Joint European Telescope for X-ray astronomy (JET-X) as a substitute optic, establishing an initial flight for the gratings and electronics on board. A pathfinder flight will reduce risk and gain insight for a full OGRE launch which will fly mono-crystalline silicon optics for the first time. Through an extensive characterization campaign for JET-X, the mono-crystalline silicon optics, EM-CCDs and a reflection grating, we have measured the performance of the OGRE spectrometer for its pathfinder flight. We confirm the continued ability of the JET-X optic, and that both the OGRE and Pathfinder OGRE spectrometers are capable of meeting the science requirement of R > 1500. Additionally, we motivate that with more detailed analysis, even higher spectral resolutions could be possible, alongside a result for the resolution of the grating itself.
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 Off-plane Grating Rocket Experiment is a soft X-ray grating spectrometer payload to be launched on a suborbital rocket. The spectrometer will use three technologies – monocrystalline silicon X-ray optics (NASA Goddard Space Flight Center), X-ray reflection gratings (The Pennsylvania State University), and electron-multiplying CCDs (XCAM Ltd., The Open University) – to achieve the highest performance on-sky soft X-ray spectrum to date when launched. To realize this performance, not only must each of the three individual spectrometer components perform at their required level, but these components also must be aligned to one another to the required tolerances and integrated into the payload. In this manuscript, we report on the alignment and integration plan for each component within the spectrometer.
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.
The Off-plane Grating Rocket Experiment (OGRE) is a soft x-ray grating spectrometer to be flown on a suborbital rocket. The payload is designed to obtain the highest-resolution soft x-ray spectrum of Capella to date with a resolution goal of R ( λ / Δλ ) > 2000 at select wavelengths in its 10 to 55 Å bandpass of interest. The optical design of the spectrometer realizes a theoretical maximum resolution of R ≈ 5000, but this performance does not consider the finite performance of the individual spectrometer components, misalignments between components, and in-flight pointing errors. These errors all degrade the performance of the spectrometer from its theoretical maximum. A comprehensive line-spread function (LSF) error budget has been constructed for the OGRE spectrometer to identify contributions to the LSF, to determine how each of these affects the LSF, and to inform performance requirements and alignment tolerances for the spectrometer. In this document, the comprehensive LSF error budget for the OGRE spectrometer is presented, the resulting errors are validated via raytrace simulations, the implications of these results are discussed, and future work is identified.
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.
The Rockets for Extended-source X-ray Spectroscopy (tREXS) are a series of sub-orbital rocket payloads that will aim to make large field-of-view spectroscopic observations of diffuse soft X-ray astrophysical objects. The tREXS payloads will passively focus X-rays onto a co-aligned array of reflection gratings, dispersing the incident X-rays onto a focal plane camera. The large focal plane requires the detector to cover a large area (100s of mm), have good quantum efficiency across the soft X-ray energy range (300 eV to 1000 eV), and survive the high-stress environment of a sub-orbital rocket launch. This paper will look at the options that were considered for this focal plane detector including Micro-Channel Plates, Charge-Coupled Devices, and CMOS detectors; including the use of commercially available camera solutions from companies such as Andor. The final choice for the focal plane camera will then be discussed in detail including the ultimate decisions behind the choice, system level integration into the payload design, and the requirements on the readout electronics, telemetry interface, and power.
Future astronomical X-ray spectrometer missions call for high spectral resolution in conjunction with high throughput. To achieve both of these requirements simultaneously, many grating elements must be aligned such that their diffraction arcs overlap at the focal plane. Methods for the alignment of reflection gratings operated in the extreme off-plane mount are being developed at The Pennsylvania State University in support of the Off-plane Grating Rocket Experiment. We report on the alignment methodology and performance tests of an aligned reflection grating module.
The Off-plane Grating Rocket Experiment (OGRE) is a soft X-ray spectroscopy suborbital rocket payload designed to obtain the highest-resolution soft X-ray spectrum of Capella to date. With a spectral resolution goal of R(λ/▵λ) < 2000 at select wavelengths in its 10-55 Å bandpass of interest, the payload will be able to study the line-dominated spectrum of Capella in unprecedented detail. To achieve this performance goal, the payload will employ three key technologies: mono-crystalline silicon X-ray mirrors developed at NASA Goddard Space Flight Center, reflection gratings manufactured at The Pennsylvania State University, and electron-multiplying CCDs developed by The Open University and XCAM Ltd. In this document, an updated optical design that can achieve the performance goal of the OGRE spectrometer and a new grating alignment concept to realize this optical design are described.
The Off-plane Grating Rocket Experiment (OGRE) is a sounding rocket payload designed to obtain a high-resolution soft X-ray spectrum of Capella. OGRE’s optical system uses new technologies including state-of-the-art X-ray optics, custom arrays of reflection gratings, and an array of EM-CCDs. Many of these technologies will be tested for the first time in flight with OGRE. To achieve the high performance that these new technologies are capable of, the payload components must be properly aligned to meet high tolerances. This paper will outline OGRE’s opto-mechanical design for achieving alignment within these tolerances. Specifically, the design of the X-ray grating arrays will be discussed.
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