The LargE Area burst Polarimeter (LEAP) is a proposed Compton scattering polarimeter that will, for the first time, measure the level of polarization for a significant number of GRBs with sufficient sensitivity to determine the magnetic field structure, composition, energy dissipation mechanism of GRB jets, and determine the prompt emission mechanism of GRBs. Once approved, LEAP will be deployed as an external payload on the International Space Station (ISS) where it will measure GRB polarization over the energy range from 50–1000 keV, perform GRB spectroscopy from 20 keV to 6 MeV, and self-sufficiently determine the source direction. LEAP is uniquely suited to fill a critical gap in our knowledge regarding GRBs, by exposing the underlying physics that governs astrophysical jets and the extreme environment surrounding newborn compact objects.
KEYWORDS: Space operations, Sensors, Equipment, Gamma radiation, Signal detection, Silicon photomultipliers, Data archive systems, Observatories, Data processing, Design
BurstCube is a 6U (10 x 20 x 30 cm) CubeSat designed to detect gamma-ray bursts (GRBs) and enable multimessenger observations, scheduled to launch in early 2024. BurstCube science is informed by the coincident detection of GRB 170817A and gravitational wave (GW) 170817, which confirmed compact binary mergers as progenitors for GRBs. Future coincident detections will also provide important context to the GW measurements - namely constraining the neutron star equation of state and testing fundamental physics, while also probing the origin of GRB prompt emission. Full sky coverage in the gamma-ray regime is needed to increase the likelihood of such measurements. Once in orbit, BurstCube will expand sky coverage while rapidly providing public alerts and localization information to the community using the Tracking and Data Relay Satellite (TDRS) and General Coordinates Network (GCN). This work will describe the current status of the mission, as well as an outline of post-launch operations, performance, and science goals.
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.
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 LargE Area Burst Polarimeter (LEAP) will radically improve our understanding of some of the most energetic phenomena in our Universe by exposing the underlying physics that governs astrophysical jets and the extreme environment surrounding newborn compact objects. LEAP will do this by making the highest fidelity polarization measurements to date of the prompt gamma-ray emission from a large sample of Gamma-Ray Bursts (GRBs). The science objectives are met with a single instrument deployed as an external payload on the ISS – a wide FOV Compton polarimeter that measures GRB polarization from 50–500 keV and GRB spectra from ~10 keV to 5 MeV. LEAP measures polarization using seven independent polarimeter modules, each with a 12x12 array of optically isolated high-Z and low-Z scintillation detectors readout by individual PMTs. LEAP is one of two NASA Missions of Opportunity proposals that are currently in a Phase A Concept Study, with a final selection due later this year.
The LargE Area burst Polarimeter (LEAP) is one of two NASA Missions of Opportunity proposals that are currently in a Phase A Concept Study, with a final selection due later this year. It is a wide Field of View (FoV) Compton polarimeter designed to study Gamma-Ray Burst (GRB) polarization over the energy range from 50- 500 keV and to measure GRB spectra in the range from 20 keV - 5 MeV. During the Phase A Concept Study, lab measurements were conducted with a small-scale (5x5) prototype polarimeter module. This included both spectral and polarization measurements with laboratory calibration sources. Here the prototype measurements and the comparisons made with simulations of the prototype detector are described. These results demonstrate the basic functionality of the LEAP design.
BurstCube aims to expand sky coverage in order to detect, localize, and rapidly disseminate information about gamma-ray bursts (GRBs). BurstCube is a ’6U’ CubeSat with an instrument comprised of 4 Cesium Iodide (CsI) scintillators coupled to arrays of Silicon photo-multipliers (SiPMs) and will be sensitive to gamma-rays between 50 keV and 1 MeV. BurstCube will assist current observatories, such as Swift and Fermi, in the detection of GRBs as well as provide astronomical context to gravitational wave (GW) events detected by LIGO, Virgo, and KAGRA. BurstCube is currently in its development phase with a launch readiness date in early 2022.
The Virtual Telescope for X-ray Observations (VTXO) will use lightweight Phase Frensel Lenses (PFLs) in a virtual X-ray telescope with ∼1 km focal length and with ∼50 milli-arcsecond angular resolution. VTXO is formed by using precision formation flying of two SmallSats: a smaller OpticsSat that houses the PFLs and navigation beacons while a larger DetectorSat contains an X-ray camera, a precision start tracker, and the propulsion for the formation flying. The baseline flight dynamics uses a highly elliptical supersynchronous orbit allow the formation to hold in an inertial frame around the 90,000 km apogee for 10 hours of the 32.5 hour orbit with nearly a year mission lifetime. VTXO’s fine angular resolution enables measuring the environments close to the central engines of bright compact X-ray sources. This X-ray imaging capability allows for the study of the effects of dust scattering near to the central objects such as Cyg X-3 and GX 5-1, for the search for jet structure near to the compact object in X-ray novae such as Cyg X-1 and GRS 1915+105, and for the search for structure in the termination shock of in the Crab pulsar wind nebula. The VTXO SmallSat and instrument designs, mission parameters, and science performance are described. VTXO development was supported as one of the selected 2018 NASA Astrophysics SmallSat Study (AS3) missions.
We report a Monte-Carlo estimation of the in-orbit performance of a cosmic X-ray polarimeter designed to be installed on the focal plane of a small satellite. The simulation uses GEANT for the transport of photons and energetic particles and results from Magboltz for the transport of secondary electrons in the detector gas. We validated the simulation by comparing spectra and modulation curves with actual data taken with radioactive sources and an X-ray generator. We also estimated the in-orbit background induced by cosmic radiation in low Earth orbit.
S. Torii, M. Hareyama, N. Hasebe, K. Kasahara, S. Kobayashi, S. Kodaira, H. Murakami, S. Ozawa, S. Udo, N. Yamashita, K. Ebisawa, H. Fuke, J. Nishimura, Y. Saito, M. Takayanagi, H. Tomida, S. Ueno, T. Yamagami, K. Hibino, S. Okuno, T. Tamura, N. Tateyama, T. Kobayashi, T. Kotani, K. Yamaoka, A. Yoshida, Y. Shimizu, M. Takita, T. Yuda, Y. Katayose, M. Shibata, E. Kamioka, A. Kubota, K. Yoshida, M. Ichimura, S. Kuramata, Y. Tunesada, T. Terasawa, H. Kitamura, Y. Uchihori, Y. Komori, K. Mizutani, K. Munakata, A. Shiomi, J. Mitchell, A. Ericsson, T. Hams, J. Krizmanic, A. Moissev, M. Sasaki, J. Ormes, M. Cherry, T. Guzik, J. Wefel, W. Binns, M. Israel, H. Krawczynski, P. Marrocchesi, M. Gagliesi, G. Bigongiari, A. Caldarone, M. Kim, R. Cecchi, P. Maestro, V. Millucci, R. Zei, C. Avanzini, T. Lotadze, A. Messineo, F. Morsani, O. Adirani, L. Bonechi, P. Papini, E. Vannuccini, J. Chan, W. Gan, T. Lu, Y. Ma, H. Wang, G. Chen
KEYWORDS: Particles, Gamma radiation, Sensors, Space telescopes, Electroluminescence, Scintillators, Signal to noise ratio, Anisotropy, Telescopes, Solar energy
We are developing the CALorimetric Electron Telescope, CALET, mission for the Japanese Experiment Module
Exposed Facility, JEM-EF, of the International Space Station. Major scientific objectives are to search for the nearby
cosmic ray sources and dark matter by carrying out a precise measurement of the electrons in 1 GeV - 20 TeV and
gamma rays in 20 MeV - several 10 TeV. CALET has a unique capability to observe electrons and gamma rays over 1
TeV since the hadron rejection power can be larger than 105 and the energy resolution better than a few % over 100 GeV.
The detector consists of an imaging calorimeter with scintillating fibers and tungsten plates and a total absorption
calorimeter with BGO scintillators. CALET has also a capability to measure cosmic ray H, He and heavy ionsi up to
1000 TeV. It also will have a function to monitor solar activity and gamma ray transients. The phase A study has
started on a schedule of launch in 2013 by H-II Transfer Vehicle (HTV) for 5 year observation.
MASSIM, the Milli-Arc-Second Structure Imager, is a mission that has been proposed for study within the context
of NASA's Astrophysics Strategic Mission Concept Studies program. It uses a set of achromatic diffractive-refractive
Fresnel lenses on an optics spacecraft to focus 5-11 keV X-rays onto detectors on a second spacecraft
flying in formation 1000 km away. It will have a point-source sensitivity comparable with that of the current
generation of major X-ray observatories (Chandra, XMM-Newton) but an angular resolution some three orders of
magnitude better. MASSIM is optimized for the study of jets and other phenomena that occur in the immediate
vicinity of black holes and neutron stars. It can also be used for studying other astrophysical phenomena on the
milli-arc-second scale, such as those involving proto-stars, the surfaces and surroundings of nearby active stars
and interacting winds.
We describe the MASSIM mission concept, scientific objectives and the trade-offs within the X-ray optics
design. The anticipated performance of the mission and possible future developments using the diffractive-refractive
optics approach to imaging at X-ray and gamma-ray energies are discussed.
The angular resolution of Chandra is close to the practical limit of grazing incidence telescopes due to the difficulty of
imparting an accurate figure and smooth surface to mirror substrates whose physical area is over two orders of
magnitude larger than their effective area. However, important scientific objectives lie beyond the reach of Chandra and
all future missions being planned by the space agencies. By transmitting X-rays diffractive and refractive optics are not
subject to the same limitations and have a superior diffraction limit. A Fresnel zone plate can be paired with a refractive
lens such that their intrinsic chromatic aberrations cancel to 1st order at a specific energy. The result is a limited but
significant energy band where the resolution is a milli arc second or better, for example, at 6 keV. Chromatic aberration
can be corrected to 2nd order by separating the diffractive and refractive elements. This configuration allows a resolution
of a few micro arc seconds. The optics are very light weight but have extremely long focal lengths resulting in a
requirement for very long distance formation flying between optics and detector spacecraft, and small fields of view.
Opacity of the refractive element imposes a lower limit upon the X-ray energy of about a few keV.
The Polarized Gamma-ray Observer (PoGO) is a new balloon-borne instrument designed to measure polarization from astrophysical objects in the 30-200 keV range. It is under development for the first flight anticipated in 2008. PoGO is designed to minimize the background by an improved phoswich configuration, which enables a detection of 10 % polarization in a 100 mCrab source in a 6--8 hour observation. To achieve such high sensitivity, low energy response of the detector is important because the source count rate is generally dominated by the lowest energy photons. We have developed new PMT assemblies specifically designed for PoGO to read-out weak scintillation light of one photoelectron (1 p.e.) level. A beam test of a prototype detector array was conducted at the KEK Photon Factory, Tsukuba in Japan. The experimental data confirm that PoGO can detect polarization of 80-85 % polarized beam down to 30 keV with a modulation factor 0.25 ± 0.05.
Phase Fresnel lenses have the same imaging properties as zone
plates, but with the possibility of concentrating all of the
incident power into the primary focus, increasing the maximum
theoretical efficiency from 11% to close to 100%. For X-rays,
and in particular for gamma-rays, large, diffraction-limited phase
Fresnel lenses can be made relatively easily. The focal length is
very long - for example up to a million kms. However, the
correspondingly high 'plate-scale' of the image means that the
ultra-high (sub-micro-arc-second) angular resolution possible with
a diffraction limited gamma-ray lens a few meters in diameter can
be exploited with detectors having mm spatial resolution. The potential of such systems for ultra-high angular resolution
astronomy, and for attaining the sensitivity improvements
desperately needed for certain other studies, are reviewed and the
advantages and disadvantages vis-a-vis alternative approaches
are discussed. We report on reduced-scale 'proof-of-principle tests' which are planned and on mission studies of the implementation of a Fresnel telescope on a space mission with lens and detector on two
spacecraft separated by one million km. Such a telescope would be
capable of resolving emission from super-massive black holes on
the scale of their event horizons and would have the sensitivity
necessary to detect gamma-ray lines from distant supernovae.
We show how diffractive/refractive optics leads to a continuum of
possible system designs between filled aperture lenses and
wideband interferometric arrays.
Fresnel lenses can focus gamma-rays by using a combination of diffraction and refraction. Such lenses (and variations on them in which the chromatic aberration is much reduced) have the potential for revolutionizing gamma-ray astronomy. Diffraction-limited lenses of several meters in size are feasible and do not require high technology for their manufacture. Focal lengths are long - up to a million kilometers - but developments in formation flying of spacecraft make possible a mission in which the lens and detector are on two separate spacecraft separated by this distance. A telescope based on these principles can have angular resolution better than a micro second of arc - sufficient to resolve the event horizon of black holes in the nucleii of AGNs. At the same time, the sensitivity can be three orders of magnitude better than that of current instrumentation.
The burst and all-sky imaging survey (BASIS) project is a proposed small explorer (SMEX) mission to image the gamma-ray sky in the 10 - 150 keV energy range with high angular and energy resolution. It will be able to determine the locations of gamma-ray bursts (GRBs) to within a few arcseconds, sending accurate positions to ground-based telescopes for simultaneous and follow-up observations within seconds of the beginning of the GRB. It will also produce all-sky maps with 30 arcsecond resolution and 2 milliCrab sensitivity. The instrument uses a two-scale coded aperture mask to modulate gamma-rays falling on a cadmium zinc telluride (CZT) detector plane consisting of both 100 micrometer pitch strip detectors and 4 mm square spectroscopy detectors. The spatial pattern of gamma-rays will be deconvolved with the mask pattern to produce an image. This paper presents results from a prototype of this system, using a mask and strip detectors to produce an image of a radioactive source. The prototype functions as expected, producing images which, when scaled to the dimensions of the proposed instrument, achieve the desired resolution.
The burst and all sky imaging survey (BASIS) is a proposed mission to provide plus or minus 3 arc-second locations of an estimated 90 gamma-ray bursts (GRBs) per year. The BASIS coded aperture imaging system requires a segmented detector plane able to detect the position of photon absorption to less than 100 microns. To develop prototype detector arrays with such fine position resolution we have fabricated many 15 mm by 15 mm by 2 mm 100 micron pitch CdZnTe strip detectors. A 2 by 2 prototype 100 micron CdZnTe strip detector array has been fabricated and has been used to test the capabilities of the BASIS imaging system. Preliminary shadowgrams of a 1 mm wide gap between two tungsten straight edges indicate that our position resolution is on the order of 69 micrometers. Both the array and imaging tests are described. A 6 by 6 element CdZnTe detector array is also being fabricated at GSFC. The assembly of this flight prototype array is discussed as well as applications for BASIS.
Yoshiyuki Takahashi, Russell Chipman, John Dimmock, Lloyd Hillman, David Lamb, Thomas Leslie, Jeffrey Weimer, Mark Christl, Gerald Fishman, Thomas Parnell, Louis Barbier, Kevin Boyce, Eric Christian, John Krizmanic, John Mitchell, Jonathan Ormes, Floyd Stecker, Donald Stilwell, Robert Streitmatter, Eugene Loh, Pierre Sokolski, Paul Sommers, Michael Cherry, John Linsley, Livio Scarsi
A concept for observation from space of the highest energy cosmic rays above 1020 eV with a satellite-borne observatory has been considered. A maximum-energy auger (air)-shower satellite (MASS) would use segmented lenses (and/or mirrors) and an array of imaging devices (about 106 pixels) to detect and record fluorescent light profiles of cosmic ray cascades in the atmosphere. The field-of-view of MASS could be extended to about (1000 km)2 so that more than 103 events per year could be observed above 1020 eV. From far above the atmosphere, MASS would be capable of observing events at all angles including near horizontal tracks, and would have considerable aperture for high energy photon and neutrino observation. With a large aperture and the spatial and temporal resolution, MASS could determine the energy spectrum, the mass composition, and arrival anisotropy of cosmic rays from 1020 eV to 1022 eV, a region hitherto not explored by ground-based detectors such as the fly's eye and air-shower arrays. MASS's ability to identify comic neutrinos and gamma rays may help providing evidence for the theory which attributes the above cut-off cosmic ray flux to the decay of topological defects.
We are studying a gamma-ray burst mission concept called burst arcsecond imaging and spectroscopy (BASIS) as part of NASA's new mission concepts for astrophysics program. The scientific objectives are to accurately locate bursts, determine their distance scale, and measure the physical characteristics of the emission region. Arcsecond burst positions (angular resolution approximately 30 arcsec, source positions approximately 3 arcsec) will be obtained for approximately 100 bursts per year using the 10 - 100 keV emission. This will allow the first deep, unconfused counterpart searches at other wavelengths. The key technological breakthrough that makes such measurements possible is the development of CdZnTe room-temperature semiconductor detectors with fine (approximately 100 micron) spatial resolution. Fine spectroscopy will be obtained between 0.2 and 150 keV. The 0.2 keV threshold will allow the first measurements of absorption in our galaxy and possible host galaxies, constraining the distance scale and host environment.
CdZnTe strip detectors have been fabricated and tested to show the ability for arc second imaging and spectroscopy. Two dimensional CdZnTe strip detectors with 100 micron pitch have been fabricated and wire bonded to readout electronics to demonstrate the ability to localize 22 to 122 keV photons to less than 100 microns. Good spectral resolution has also been achieved. The uniformity and relative efficiency of the strip detector are discussed. Radiation damage effects by intermediate energy neutrons and low energy protons on the surface and bulk performance of CdZnTe devices have been investigated and are presented. Activation and annealing of radiation effects have been seen and are discussed.
We exposed a CdZnTe detector to MeV neutrons from a 252Cf source and found no performance degradation for fluences below 1010 neutrons cm-2. Detector resolution did show significant degradation at higher neutron fluences. There is evidence of room temperature annealing of the radiation effects over time. Activation lines were observed and the responsible isotopes were identified by the energy and half-life of the lines. These radiation damage studies allow evaluation of the robustness of CdZnTe detectors in high neutron and radiation environments.
A CdZnTe strip detector array with capabilities for arc second imaging and spectroscopy is being developed for a space flight gamma-ray burst instrument. Two dimensional strip detectors with 100 micrometers pitch have been fabricated and wire bonded to readout electronics to demonstrate the ability to localize 22 to 122 keV photons to less than 100 micrometers. In addition, good spectral resolution has been achieved. The uniformity of response and relative efficiency of the strip detector will be discussed. Results form electrical characterization which include strip leakage current and strip capacitance will be presented.
We have proposed a gamma-ray burst mission concept called burst arcsecond imaging and spectroscopy (BASIS) in response to NASA's announcement for new mission concept studies. The scientific objectives are to accurately locate bursts, determine their distance scale, and measure the physical characteristics of the emission region. Arcsecond burst positions (angular resolution approximately 30 arcsec, source positions approximately 3 arcsec for greater than 10-6 erg cm-2 bursts) are obtained for about 100 bursts per year using the 10 - 200 keV emission. This allows the first deep, unconfused counterpart searches at other wavelengths. The key technological breakthrough that makes such measurements possible is the development of CdZnTe room-temperature semiconductor detectors with fine (approximately 100 micron) spatial resolution. Fine spectroscopy is obtained between 0.2 keV and 200 keV. The 0.2 keV threshold allows the first measurements of absorption in our galaxy and possible host galaxies, constraining the distance scale and host environment. The mission concept and its scientific objectives are described.
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