Versatile Optics for X-ray Imaging (VOXI) is a technology that enables a wide range of missions and opens up new opportunities for scientific research over multiple disciplines including fundamental physics, heliophysics, astrophysics, lunar and planetary science, and laboratory physics. VOXI is well-suited to SmallSats, which have become powerful platforms from which to conduct leading scientific investigations and cutting-edge technology developments at low cost with rapid turn-arounds. At the Center for Astrophysics | Harvard and Smithsonian, in collaboration with other institutions, we have developed VOXI, a Wolter-I Xray telescope with a focal length of < 1.5 m. In this paper we describe the potential of these optics, and the applications for VOXI optics considered to date.
HSP was selected for the NASA Astrophysics Science SmallSat Study (AS3) program
as a SmallSat mission concept that will be proposed for a 1 – 2 year science mission to demonstrate performance and cost goals to enable a future Explorer-class SmallSat Constellation mission for the first simultaneous full-sky imager with 2X finer resolution. HSP is a 36 x 36deg (FWHM) coded aperture telescope with 16 x 16 CdZnTe detectors, each 20 x 20 x 3mm with 32 x 32 0.6mm pixels and ~1.5keV energy resolution. The 1024 cm^2 HSP imaging detector array views the sky through the Tungsten coded aperture mask (0.7 mm pixels) at 68cm, providing 4’ imaging and <30” source positions over the 3 – 200 keV band. This is mounted on a Blue Canyon Technologies (BCT) SmallSat (S5) bus, with ~10arcsec pointing and star camera aspect, extends the capabilities of Swift/BAT and INTEGRAL/IBIS. HSP will promptly localize long and short GRBs and outbursts of X-ray transients: from nearby M dwarf flares, to BH-LMXB outbursts, Blazar flares and Jetted TDEs. HSP will daily-monitor the Galactic Bulge and adjacent Galactic plane and > 2 nearby OB association regions for 1 yr, providing high cadence light curves of black hole X-ray binaries (with low and high mass companions) in the Galaxy. HSP matches the on-axis sensitivity of Swift/BAT in the 15 – 200 keV band with 5X finer spatial resolution, and the simultaneous 3 – 15 keV imaging and spectra surpass MAXI with 15X finer spatial resolution, all within an ESPA class mission in LEO at ~500-600 km and <~30 deg inclination.
The first detected exoplanets found were "hot Jupiters"; these are large Jupiter-like planets in close orbits with their host star. The stars in these so-called "hot Jupiter systems" can have significant X-ray emission and the X-ray flux likely changes the evolution of the overall star-planetary system in at least two ways: (1) the intense high energy flux alters the structure of the upper atmosphere of the planet - in some cases leading to significant mass loss; (2) the angular momentum and magnetic field of the planet induces even more activity on the star, enhancing its X-rays, which are then subsequently absorbed by the planet. If the alignment of the systems is appropriate, the planet will transit the host star. The resulting drop in flux from the star allows us to measure the distribution of the low-density planetary atmosphere. We describe a science mission concept for a SmallSat Exosphere Explorer of hot Jupiters (SEEJ; pronounced "siege"). SEEJ will monitor the X-ray emission of nearby X-ray bright stars with transiting hot Jupiters in order to measure the lowest density portion of exoplanet atmospheres and the coronae of the exoplanet hosts. SEEJ will use revolutionary Miniature X-ray Optics (MiXO) and CMOS X-ray detectors to obtain sufficient collecting area and high sensitivity in a low mass, small volume and low-cost package. SEEJ will observe scores of transits occurring on select systems to make detailed measurements of the transit depth and shape which can be compared to out-of-transit behavior of the target system. The depth and duration of the flux change will allow us to characterize the exospheres of multiple hot Jupiters in a single year. In addition, the long baselines (covering multiple stellar rotation periods) from the transit data will allow us to characterize the temperature, flux and flare rates of the exoplanet hosts at an unprecedented level. This, in turn, will provide valuable constraints for models of atmospheric loss. In this contribution we outline the science of SEEJ and focus on the enabling technologies Miniature X-ray Optics and CMOS X-ray detectors.
The High-Energy X-ray Probe (HEX-P) is a probe-class mission concept that will extend the reach of broadband (2-200 keV) X-ray observations, with 40 times the sensitivity of any previous mission in the 10-80 keV band and 10,000 times the sensitivity of any previous mission in the 80-200 keV band. HEX-P addresses key NASA science goals and is an important complement to ESA's L-class Athena mission. Working in coordination with Athena HEX-P will provide continuum measurements that are essential for interpreting Athena spectra. With angular resolution improved by more than an order of magnitude relative to NuSTAR, HEX-P will carry out an independent program aimed at addressing questions unique to the high energy X-ray band, such as the nature of the source that powers Active Galactic Nuclei, the evolution of black holes in obscured environments, and understanding of how compact binary systems form, evolve and influence galactic systems. With heritage from NuSTAR, HEX-P can be executed within the next decade with a budget less than double that of a Medium class Explorer (MIDEX) mission.
The Extreme Physics Explorer (EPE) is a concept timing/spectroscopy mission that would use micro-channel plate
optics (MCPO) to provide 4m2 effective area focused to ~1 arc-min onto an X-ray calorimeter. We describe science
drivers for such a mission, possible designs for the large area MCPO needed for EPE, and the challenges of the large
area MCPO design.
The WHIMex X-ray observatory will provide an order of magnitude improvement in sensitivity and spectroscopic
resolution, ushering in a new era in astrophysics. With resolution ≥ 4,000 and collecting area 250 cm2 in the 0.2-
0.8 keV band, WHIMex will greatly extend the spectroscopic discoveries of Chandra and XMM with a low-cost,
highly-productive Explorer mission. WHIMex's spectra will provide a wealth of new information on the physical
conditions of baryonic matter from the local regions of our Galaxy out to the Cosmic Web and the large-scale
structures of the Universe. This baryonic matter is thought to result from gravitational collapse of moderately over-dense,
dark-matter filaments of the Cosmic Web. The chemical enrichment of the Cosmic Web appears to arise from
galactic super winds and early generations of massive stars. WHIMex will test these theories, distinguish between
competing models, and provide new insights into galaxy evolution and the structure of the universe High-resolution
X-ray spectroscopy was identified by the ASTRO 2010 decadal survey as a high-priority capability in the coming
decade for a wide variety of science goals. Unfortunately, no other planned mission can address this science until
IXO flies, no earlier than the late 2020s. WHIMex achieves its high level of performance in a single-instrument,
affordable package using X-ray optical technologies developed for IXO and NuSTAR by academic, industrial and
government research centers. The technology readiness levels of all the components are high. We plan to build an
optical test module and raise the optical system readiness to TRL 6 during Phase A.
High-energy astrophysics is a relatively young scientific field, made possible by space-borne telescopes. During the
half-century history of x-ray astronomy, the sensitivity of focusing x-ray telescopes-through finer angular resolution
and increased effective area-has improved by a factor of a 100 million. This technological advance has enabled
numerous exciting discoveries and increasingly detailed study of the high-energy universe-including accreting (stellarmass
and super-massive) black holes, accreting and isolated neutron stars, pulsar-wind nebulae, shocked plasma in
supernova remnants, and hot thermal plasma in clusters of galaxies. As the largest structures in the universe, galaxy
clusters constitute a unique laboratory for measuring the gravitational effects of dark matter and of dark energy. Here,
we review the history of high-resolution x-ray telescopes and highlight some of the scientific results enabled by these
telescopes. Next, we describe the planned next-generation x-ray-astronomy facility-the International X-ray
Observatory (IXO). We conclude with an overview of a concept for the next next-generation facility-Generation X.
The scientific objectives of such a mission will require very large areas (about 10000 m2) of highly-nested lightweight
grazing-incidence mirrors with exceptional (about 0.1-arcsecond) angular resolution. Achieving this angular resolution
with lightweight mirrors will likely require on-orbit adjustment of alignment and figure.
We present simulated observations of surface features on Red Supergiant (RSG) stars and clumpy dust structures
surrounding Active Galactic Nuclei (AGN) with the Magdalena Ridge Observatory Interferometer (MROI). These
represent two of the classes of astrophysical targets enumerated in the MROI Key Science Mission that are typical of the
types of complex astrophysical phenomena that the MROI has been designed to image. The simulations are based on
source structures derived from recent theoretical models and include both random and systematic noise on the measured
Fourier data (visibility amplitudes and closure phases) consistent with our expectations for typical such targets observed
with the MROI. Image reconstructions, obtained using the BSMEM imaging package, are presented for 4-, 6- and 8-
telescope implementations of the array. Although a rudimentary imaging capability is demonstrated with only 4
telescopes, the detailed features of targets are only reliably determined when at least 6 telescopes are present. By the tine
8 telescope are used, the reconstructed images are sufficiently faithful to allow the discrimination between competing
models, confirming the design goal of the MROI, i.e. to offer model-independent near-infrared imaging on sub-milliarcsecond
scales.
There is a growing need for multiply nested large area X-ray mirrors with very fine angular resolution in future X-ray
astrophysics experiments. Despite of promising results of several exploited technologies, it is not demonstrated yet that
these technologies will provide the required angular resolutions of order of few arcsec. The alternative approach
described in this paper is the method of active X-ray optics. In addition, active approaches based on computer control
may be applied directly during manufacturing of advanced X-ray optics elements. We propose these methods as an
alternative for the IXO project recently under study by ESA/NASA/JAXA.
Generation-X will be an X-ray observatory with 50 m2
collecting area at 1 keV and 0.1" angular resolution. A key
concept to enable such a dramatic improvement in angular resolution is
that the mirror figure will be adjusted on-orbit; e.g., via piezo-electric
actuators deposited on the back side of very thin glass and imparting
strains in a bi-morph configuration. To make local adjustments to the
individual mirror shells we must employ an imaging detector far
forward of the focal surface, so that rays from the individual shells
can be measured as distinct rings. We simulate this process on a few
representative shells via ray-traces of perfect optics, perturbed
axially by low order Legendre polynomial terms. This elucidates some of
the requirements for the on-orbit measurements, and on possible
algorithms to perform the on-orbit adjustment with acceptably rapid
convergence.
We report on the prospects for the study of the first stars, galaxies and black holes with the Generation-X Mission.
Generation-X is a NASA "Vision Mission" which completed preliminary study in lat e2006. Generation-X was approved
in February 2008 as an Astrophysics Strategic Mission Concept Study (ASMCS) and is baselined as an X-ray
observatory with 50 square meters of collecting area at 1 keV (500 times larger than Chandra) and 0.1 arcsecond angular
resolution (several times better than Chandra and 50 times better than the Constellation-X resolution goal). Such a high
energy observatory will be capable of detecting the earliest black holes and galaxies in the Universe, and will also study
the chemical evolution of the Universe and extremes of density, gravity, magnetic fields, and kinetic energy which
cannot be created in laboratories. A direct signature of the formation of the first galaxies, stars and black holes is
predicted to be X-ray emission at characteristic X-ray temperatures of 0.1-1 keV from the collapsing proto-galaxies
before they cool and form the first stars.
Antonella Fruscione, Jonathan McDowell, Glenn Allen, Nancy Brickhouse, Douglas Burke, John Davis, Nick Durham, Martin Elvis, Elizabeth Galle, Daniel Harris, David Huenemoerder, John Houck, Bish Ishibashi, Margarita Karovska, Fabrizio Nicastro, Michael Noble, Michael Nowak, Frank Primini, Aneta Siemiginowska, Randall Smith, Michael Wise
The CIAO (Chandra Interactive Analysis of Observations) software package was first released in 1999 following the launch of the Chandra X-ray Observatory and is used by astronomers across the world to analyze Chandra data as well as data from other telescopes. From the earliest design discussions, CIAO was planned as a general-purpose scientific data analysis system optimized for X-ray astronomy, and consists mainly of command line tools (allowing easy pipelining and scripting) with a parameter-based interface layered on a flexible data manipulation I/O library. The same code is used for the standard Chandra archive pipeline, allowing users to recalibrate their data in a consistent way. We will discuss the lessons learned from the first six years of the software's evolution. Our initial approach to documentation evolved to concentrate on recipe-based "threads" which have proved very successful. A multi-dimensional abstract approach to data analysis has allowed new capabilities to be added while retaining existing interfaces. A key requirement for our community was interoperability with other data analysis systems, leading us to adopt standard file formats and an architecture which was as robust as possible to the input of foreign data files, as well as re-using a number of external libraries. We support users who are comfortable with coding themselves via a flexible user scripting paradigm, while the availability of tightly constrained pipeline programs are of benefit to less computationally-advanced users. As with other analysis systems, we have found that infrastructure maintenance and re-engineering is a necessary and significant ongoing effort and needs to be planned in to any long-lived astronomy software.
Some tests of fundamental physics - the equation of state at supra-nuclear densities, the metric in strong gravity,
the effect of magnetic fields above the quantum critical value - can only be measured using compact astrophysical
objects: neutron stars and black holes. The Extreme Physics Explorer is a modest sized (~500 kg) mission that
would carry a high resolution (R ~300) X-ray spectrometer and a sensitive X-ray polarimeter, both with high
time resolution (~5 μs) capability, at the focus of a large area (~5 sq.m), low resolution (HPD~1 arcmin) X-ray
mirror. This instrumentation would enable new classes of tests of fundamental physics using neutron stars and
black holes as cosmic laboratories.
X-rays provide one of the few bands through which we can study the epoch of reionization, when the first galaxies,
black holes and stars were born. To reach the sensitivity required to image these first discrete objects in the
universe needs a major advance in X-ray optics. Generation-X (Gen-X) is currently the only X-ray astronomy
mission concept that addresses this goal. Gen-X aims to improve substantially on the Chandra angular resolution
and to do so with substantially larger effective area. These two goals can only be met if a mirror technology
can be developed that yields high angular resolution at much lower mass/unit area than the Chandra optics,
matching that of Constellation-X (Con-X). We describe an approach to this goal based on active X-ray optics
that correct the mid-frequency departures from an ideal Wolter optic on-orbit. We concentrate on the problems
of sensing figure errors, calculating the corrections required, and applying those corrections. The time needed
to make this in-flight calibration is reasonable. A laboratory version of these optics has already been developed
by others and is successfully operating at synchrotron light sources. With only a moderate investment in these
optics the goals of Gen-X resolution can be realized.
The new frontier in astrophysics is the study of the very first stars, galaxies and black holes in the early Universe. These objects are beyond the grasp of the current generation of X-ray telescopes such as Chandra, and so the Generation-X Vision Mission has been proposed as an X-ray observatory which will be capable of detecting these earliest objects. Xray imaging and spectroscopy of such distant objects will require an X-ray telescope with large collecting area and high angular resolution. The Generation-X concept has 100 m2 collecting area at 1 keV (1000 times larger than Chandra) and 0.1 arcsecond angular resolution (several times better than Chandra and 50 times better than the resolution goal for Constellation-X). The baseline mission involves four 8 m diameter telescopes operating at Sun-Earth L2. Such large telescopes will require either robotic or human-assisted in-flight assembly. To achieve the required effective area with launchable mass, very lightweight grazing incidence X-ray optics must be developed, having an areal density 100 times lower than in Chandra, with perhaps 0.1 mm thick mirrors requiring on-orbit figure control. The suite of available detectors for Generation-X should include a large-area high resolution imager, a cryogenic imaging spectrometer and a grating spectrometer.
Large collecting area x-ray telescopes are designed to study the early Universe, trace the evolution of black holes, stars and galaxies, study the chemical evolution of the Universe, and study matter in extreme environments. The Constellation-X mission (Con-X), planned for launch in 2016, will provide ~ 104 cm2 collecting area with 15 arc-sec resolution, with a goal of 5 arc-sec. Future missions require larger collecting area and finer resolution. Generation-X (Gen-X), a NASA Visions Mission, will achieve 100 m2 effective area at 1 keV and angular resolution of 0.1 arc-sec, half power diameter. We briefly describe the Con-X flowdown of imaging requirements to reflector figure error. To meet requirements beyond Con-X, Gen-X optics will be thinner and more accurately shaped than has ever been accomplished. To meet these challenging goals, we incorporate for the first time active figure control with grazing incidence optics. Piezoelectric material will be deposited in discrete cells directly on the back surface of the optical segments, with the strain directions oriented parallel to the surface. Differential strain between the two layers of the mirror causes localized bending in two directions, enabling local figure control. Adjusting figure on-orbit eases fabrication and metrology. The ability to make changes to mirror figure adds margin by mitigating risk due to launch-induced deformations and/or on-orbit degradation. We flowdown the Gen-X requirements to mirror figure and four telescope designs, and discuss various trades between the designs.
We present a mission concept for high resolution X-ray
spectroscopy with a resolving power, R ~6000. This resolution is physics-driven, since it allows the thermal widths of coronal X-ray lines to be measured, and astrophysics-driven, since 50km/s resolves internal galaxy motions, and galaxy motions within larger structures.
Such a mission could be small and have a rapid response allowing
us to 'X-ray the Universe' using the afterglows of Gamma-ray Bursts (GRBs) as strong background sources of X-rays, and so illuminate the `Cosmic Web'. The Cosmic Web is predicted to contain most of the normal matter (baryons) in the nearby Universe.
Four reflection, grazing incidence X-ray optics offer the possibility of broad band (0.1-10.0 keV) X-ray telescopes that fit within the physical envelope of NASA's Small and Medium Explorer mission. We describe a short focal length (4 m) optical design with arcsec imagery over a 1 degree(s) field of view and good efficiency in the Fe-K band (6.4-7.1 keV).
KEYWORDS: Local area networks, Optical design, Ray tracing, Optimization (mathematics), Algorithms, Annealing, Astronomical telescopes, Software development, Grazing incidence, Data communications
The downhill simplex and simulated annealing algorithms are powerful design tools for optical systems that do not yield to analytic methods of optimization. Use of these numerical techniques have been frustrated by the shortage of computational resources available to investigators. To tap the latent computational resources available in even moderate sized local area networks (LAN's), we have developed software to operate flexibly, a LAN composed of UNIX workstations as a distributed processor for optical design optimization. We have developed a general purpose remote procedure call generator and subroutine library which allow simple specification and use of existing subprograms as remote procedures. This software provides a mechanism for modifying or developing large scientific and engineering applications with inherent parallelism for distributed processing on LAN's. We discuss the performance, bandwidth, and adaptability of this software as applied to the problem of grazing incidence optics design using the simulated annealing algorithm.
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