We report on the on-orbit performance of the Glowbug instrument, which operated on the International Space Station (ISS) from March 2023 to April 2024. Glowbug is a NASA Astrophysics Research and Analysis (APRA) funded instrument built by the U.S. Naval Research Laboratory (NRL) in Washington, DC, and is the pathfinder instrument for the upcoming NASA StarBurst Multimessenger Pioneers mission. Glowbug was launched to the ISS on the 27th Commercial Resupply Services mission operated by SpaceX (SpX-27) as part of the Department of Defense Space Test Program (STP) H9 pallet. Glowbug’s primary science objective is the detection and localization of short Gamma-Ray Bursts (GRBs), which are the result of mergers of stellar binaries involving a neutron star with either another neutron star or a black hole. Detection is enabled by 12 large area (150mm x 150mm), inorganic scintillator panels (thallium-doped cesium iodide, CsI:Tl), arrayed on the surface of a half cube. Each panel is read out on one edge by a 1x21 array of onsemi J-series 6mm x 6mm silicon photomultipliers (SiPMs). Additionally, within the half cube, resides two inorganic scintillators, Cs2LiLaBr6:Ce (CLLB), and a small plastic (EJ-200) scintillator on the exterior used as an South Atlantic Anomaly (SAA) entry and exit detector, both of which are read out by an array of SiPMs on one face of each detector unit. We discuss the Glowbug on-orbit results for one year’s worth of data, in terms of on-orbit operations, SiPM performance in low-earth orbit (LEO), and GRB detections.
ComPair is a prototype gamma-ray telescope for the development of key technologies for next-generation gammaray detectors consisting of four subsystems: a 10-layer double-sided silicon strip detector tracker, a cadmium zinc telluride calorimeter, a cesium iodide calorimeter, and a plastic anti-coincidence detector (ACD). The ACD acts as an active shield to veto charged particle events and consists of 5 plastic scintillating panels. ComPair was launched as a balloon payload from Ft. Sumner, New Mexico and completed a 6-hour flight on August 27, 2023. Here we detail the design and calibration of the ComPair ACD, and report on the ACD’s veto efficiency and other performance metrics during the ComPair flight.
Many questions posed in the Astro2020 Decadal survey in both the New Messengers and New Physics and the Cosmic Ecosystems science themes require a gamma-ray mission with capabilities exceeding those of existing (e.g. Fermi, Swift) and planned (e.g. COSI) observatories. ComPair, the Compton Pair telescope, is a prototype of such a next-generation gamma-ray mission. It had its inaugural balloon flight from Ft. Sumner, New Mexico in August 2023. To continue the goals of the ComPair project to develop technologies that will enable a future gamma-ray mission, the next generation of ComPair (ComPair-2) will be upgraded to increase the sensitivity and low-energy transient capabilities of the instrument. These advancements are enabled by AstroPix, a silicon monolithic active pixel sensor, in the tracker and custom dual-gain silicon photomultipliers and front-end electronics in the calorimeter. This effort builds on design work for the All-sky Medium Energy Gamma-ray Observatory eXplorer (AMEGO-X) concept that was submitted the 2021 MIDEX Announcement of Opportunity. Here we describe the ComPair-2 prototype design and integration and testing plans to advance the readiness level of these novel technologies.
The ComPair balloon instrument is a prototype gamma-ray telescope that aims to further develop technology for observing the gamma-ray sky in the MeV regime. ComPair combines four detector subsystems to enable parallel Compton scattering and pair-production detection, critical for observing in this energy range. This includes a 10 layer double-sided silicon strip detector tracker, a virtual Frisch grid low energy CZT calorimeter, a high energy CsI calorimeter, and a plastic scintillator anti-coincidence detector. The inaugural balloon flight successfully launched from the Columbia Scientific Balloon Facility site in Fort Sumner, New Mexico, in late August 2023, lasting approximately 6.5 hours in duration. In this proceeding, we discuss the development of the ComPair balloon payload, the performance during flight, and early results.
The ComPair gamma-ray telescope is a technology demonstrator for a future gamma-ray telescope called the All-sky Medium Energy Gamma-ray Observatory (AMEGO). The instrument is composed of four subsystems, a double-sided silicon strip detector, a virtual Frisch grid CdZnTe calorimeter, a CsI:Tl based calorimeter, and an anti-coincidence detector (ACD). The CsI calorimeter's goal is to measure the position and energy deposited from high-energy events. To demonstrate the technological readiness, the calorimeter has flown onboard a NASA scientific balloon as part of the GRAPE-ComPair mission and accumulated around 3 hours of float time at an altitude of 40 km. During the flight, the CsI calorimeter observed background radiation, Regener-Pfotzer Maximum, and several gamma-ray activation lines originating from aluminum.
In this paper we report on the development of Glowbug-2: a gamma-ray transient instrument for the International Space Station (ISS). Glowbug-2 is the next iteration of instrumentation for detecting and localizing gamma-ray transients, in particular Gamma Ray Bursts (GRBs), being developed and built by the U.S. Naval Research Laboratory (NRL). This iteration of Glowbug follows the successful deployment and operation of the Glowbug-1 instrument on the ISS [1,2], located on the Japanese Experiment Module – Exposed Facility Unit (JEM-EFU) from March 2023 to April 2024. Glowbug-2 consists of four large area, panel scintillation detectors with edge read out via an array of silicon photomultipliers (SiPMs), on the Department of Defense Space Test Program (DoD STP) H-11 pallet. The launch to the Columbus External Payload Facility SOZ on the ISS is expected in late 2025. The scintillation crystal detector units (CDUs) are the same design as the units to be flown on the upcoming NASA StarBurst Multimessenger Pioneers mission. Glowbug-2 will serve as a science enhancement and risk reduction instrument for the StarBurst mission. Each scintillation panel views the sky at a 45° angle (with respect to the pallet), with each detector facing orthogonal viewing directions, for all sky coverage not occulted by the earth. This work presents the science Glowbug-2 will address, the instrument concept and design, and simulated and laboratory instrument performance metrics.
The GAGG Radiation Instrument (GARI) is designed to space-qualify a compact, high-sensitivity gamma-ray spectrometer for astrophysical and defense applications and has completed over one year of operations on the International Space Station (ISS). The on-orbit activation of the GAGG crystal induced by the radiation background was measured. Characteristic gamma-ray lines present in the on-orbit spectra were compared to ground-based tests for identification. The radiation background, including the particle-induced internal activation of the crystal, affects the sensitivity of the instrument. We also show the degradation in the performance of the silicon photomultiplier (SiPM) readout (known to be sensitive to radiation damage). Results shown here will be useful in predicting the performance of larger instruments that use GAGG scintillator technology for gamma-ray spectroscopy.
The Neutron Radiation Detection Instrument-1A (NeRDI-1A) is a neutron sensor on the International Space Station (ISS) as part of the Department of Defense Space Test Program (STP) mission STP-H9. NeRDI-1A uses the scintillator Tl2LiYCl6:Ce as well as three Domino microstructured semiconductor neutron detectors (MSNDs) with varying levels of moderation and an EJ-270 plastic scintillator. The primary objective of NeRDI-1A is to space qualify TLYC and MSND detectors by studying the effects of on-orbit radiation background on the performance of these detectors over the nominal one-year mission. NeRDI-1A was launched to the ISS on 15 March 2023 GMT aboard SpX-27.
The All-sky Medium Energy Gamma-ray Observatory eXplorer (AMEGO-X) is designed to identify and characterize gamma rays from extreme explosions and accelerators. The main science themes include supermassive black holes and their connections to neutrinos and cosmic rays; binary neutron star mergers and the relativistic jets they produce; cosmic ray particle acceleration sources including galactic supernovae; continuous monitoring of other astrophysical events and sources over the full sky in this important energy range. AMEGO-X will probe the medium energy gamma-ray band using a single instrument with sensitivity up to an order of magnitude greater than previous telescopes in the energy range 100 keV to 1 GeV that can be only realized in space. During its 3-year baseline mission, AMEGO-X will observe nearly the entire sky every two orbits, building up a sensitive all-sky map of gamma-ray sources and emissions. AMEGO-X was submitted in the recent 2021 NASA MIDEX announcement of opportunity.
In this paper we describe ProtoGECCO–a prototype instrument for the Galactic Explorer with a Coded aperture mask and Compton Telescope (GECCO). ProtoGECCO is comprised of two main imaging calorimeters. The top calorimeter is an array of cadmium zinc telluride (CZT); the bottom calorimeter is an array of high-light yield Gd3Al2Ga3O12:Ce (GAGG) fingers with silicon photomultiplier (SiPM) readout. The calorimeters are surrounded by a thallium-doped cesium iodide (CsI:Tl) active shield. ProtoGECCO employs the techniques of both coded aperture imaging and a Compton telescope. The main goals of the prototype are to further develop the instrument technology, thereby raising the technical readiness level (TRL), and to fly on a high-altitude balloon from Fort Sumner, NM. The results of this work are directly applicable to future space instruments that require detectors with large area; excellent spatial, energy, and angular resolution; and high detection efficiency. Such future missions will address problems in the MeV domain of gamma-ray astronomy—one of the most underexplored windows on the universe.
In this paper we describe the characterization of the Glowbug instrument. Glowbug is a gamma-ray telescope for gamma ray bursts (GRBs) and other transients in the 50 keV to 2 MeV band funded by the NASA Astrophysics Research and Analysis (APRA) program. Built by the U.S. Naval Research Laboratory, the instrument will be launched to the International Space Station (ISS) by the Department of Defense (DOD) Space Test Program (STP) in early 2023. Glowbug’s primary science objective is the detection and localization of short GRBs, which are the result of mergers of stellar binaries involving a neutron star with either another neutron star or a black hole. While the instrument is designed to complement existing GRB detection systems, it serves as a technology demonstrator for future networks of sensitive, low-cost gamma-ray transient detectors that provide all-sky coverage and improved localization of such events. Of greatest interest are the binary neutron star systems within the detection horizon of ground-based gravitational-wave interferometers. In a full mission life, Glowbug will detect dozens of short GRBs and provide burst spectra, light curves, and positions for gamma-ray context in multi-wavelength and multi-messenger studies of these merger events. We will present the current state of Glowbug, which will include the hardware development, calibration, environmental testing, simulations, and expected on-orbit sensitivity.
There is a growing interest in the science uniquely enabled by observations in the MeV range, particularly in light of multi-messenger astrophysics. The Compton Pair (ComPair) telescope, a prototype of the AMEGO Probe-class concept, consists of four subsystems that together detect and characterize gamma rays in the MeV regime. A double-sided strip silicon Tracker gives a precise measure of the first Compton scatter interaction and tracks pair-conversion products. A novel cadmium zinc telluride (CZT) detector with excellent position and energy resolution beneath the Tracker detects the Compton-scattered photons. A thick cesium iodide (CsI) calorimeter contains the high-energy Compton and pair events. The instrument is surrounded by a plastic anti-coincidence (ACD) detector to veto the cosmic-ray background. In this work, we will give an overview of the science motivation and a description of the prototype development and performance.
The GAGG Radiation Instruments (GARI), two identical instruments, are designed to space-qualify new gamma-ray detector technology for space-based astrophysical and defense applications. The detector technology offers improved energy resolution, lower power consumption and reduced size compared to similar systems. Each identical GARI instrument consists of a two cerium-doped gadolinium aluminum gallium garnet (GAGG (Gd3(Al,Ga)5O12 :Ce)) scintillation detectors. The crystals have an energy resolution of 4.2% at 662 keV (specified by the manufacturer) compared to the 6.5% of traditional sodium iodide, and the material has found widespread use in medical imaging applications. GAGG is also unique in the fact that it is rugged (resistant to harsh environments) and one of the few non-hygroscopic scintillators available. GARI’s objective is to study the on-orbit internal activation of the GAGG material and measure the performance of the silicon photomultiplier (SiPM) readouts over its 1-year mission. The combined detectors measure the gamma-ray spectrum over the energy range of 0.02 - 8 MeV. The GARI mission payoff is a space-qualified compact, high-sensitivity gamma-ray spectrometer with improved energy resolution relative to previous sensors. Applicable studies in solar physics and astrophysics include solar flares, Gamma Ray Bursts, novae, supernovae, and the synthesis of the elements. Department of Defense (DoD) and security applications are also possible. Construction of the GARI instruments has been completed, and both instruments are being integrated onto their respective platforms. Both instruments are expected to launch in December of 2021 onboard STP-H7 and STP-H8. This work discusses the objectives, design details and mission concept of operations of the GARI spectrometers.
The SIRI line of instruments is designed to space-qualify new space-based, gamma-ray detector technology for Department of Defense (DoD) and astrophysics applications. SIRI-2’s primary objective is to demonstrate the performance of europium-doped strontium iodide (SrI2:Eu) gamma-ray detection technology with sufficient active area for DoD operational needs. Secondary scientific objectives include understanding the internal background of SrI2:Eu in the space radiation environment, and studying transient phenomena, such as solar flares. The primary detector array of the SIRI instrument consists of seven hexagonal europium-doped strontium iodide (SrI2:Eu) scintillation detectors 3.81 cm by 3.81 cm, with a combined active area of 66 cm2. SIRI-2’s primary detectors have an energy resolution of ~4% at 662 keV. SIRI-2 is expected to operate in the high gamma-ray background of a geosynchronous orbit and the instrument includes a number of features to both passively and actively suppress the unique background of the outer Van Allen belts. Construction and environmental testing of the SIRI-2 instrument has been completed, and it is currently awaiting integration onto the spacecraft bus. The expected launch date is Aug 2020 onboard the Space Test Program’s STPSat-6.
This paper will focus on next-generation inorganic scintillation detectors that could be used to study neutral emission from the high-energy Sun. Recent developments in detector technology have yielded candidate materials for future heliophysics missions, namely elpasolites (Cs2LiYCl6:Ce – CLYC and Cs2LiLaBr6:Ce – CLLB). At a modest cost, these detectors yield superior spectroscopic performance compared to previously used materials (NaI:Tl and CsI:Tl). Additionally, elpasolites can detect and measure thermal to fast (<10 MeV) neutrons, simultaneously with γ rays. In the following sections, we discuss: the importance for measuring neutral emission from the Sun, laboratory performance of candidate scintillators and novel light readout devices, a proposed instrument concept, and the expected response to a γ-ray line-producing and neutron-producing solar flares from the vantage points of 1 AU, 0.3 AU, and 0.04 AU.
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