Arcus, a Medium Explorer (MIDEX) mission, was selected by NASA for a Phase A study in August 2017. The observatory provides high-resolution soft X-ray spectroscopy in the 12-50Å bandpass with unprecedented sensitivity: effective areas of >450 cm2 and spectral resolution >2500. The Arcus key science goals are (1) to measure the effects of structure formation imprinted upon the hot baryons that are predicted to lie in extended halos around galaxies, groups, and clusters, (2) to trace the propagation of outflowing mass, energy, and momentum from the vicinity of the black hole to extragalactic scales as a measure of their feedback and (3) to explore how stars, circumstellar disks and exoplanet atmospheres form and evolve. Arcus relies upon the same 12m focal length grazing-incidence silicon pore X-ray optics (SPO) that ESA has developed for the Athena mission; the focal length is achieved on orbit via an extendable optical bench. The focused X-rays from these optics are diffracted by high-efficiency Critical-Angle Transmission (CAT) gratings, and the results are imaged with flight-proven CCD detectors and electronics. The power and telemetry requirements on the spacecraft are modest. Mission operations are straightforward, as most observations will be long (~100 ksec), uninterrupted, and pre-planned, although there will be capabilities to observe sources such as tidal disruption events or supernovae with a ~3 day turnaround. Following the 2nd year of operation, Arcus will transition to a proposal-driven guest observatory facility.
Arcus will be proposed to the NASA Explorer program as a free-flying satellite mission that will enable high-resolution soft X-ray spectroscopy (8-50) with unprecedented sensitivity – effective areas of >500 sq cm and spectral resolution >2500. The Arcus key science goals are (1) to determine how baryons cycle in and out of galaxies by measuring the effects of structure formation imprinted upon the hot gas that is predicted to lie in extended halos around galaxies, groups, and clusters, (2) to determine how black holes influence their surroundings by tracing the propagation of out-flowing mass, energy and momentum from the vicinity of the black hole out to large scales and (3) to understand how accretion forms and evolves stars and circumstellar disks by observing hot infalling and outflowing gas in these systems. Arcus relies upon grazing-incidence silicon pore X-ray optics with the same 12m focal length (achieved using an extendable optical bench) that will be used for the ESA Athena mission. The focused X-rays from these optics will then be diffracted by high-efficiency off-plane reflection gratings that have already been demonstrated on sub-orbital rocket flights, imaging the results with flight-proven CCD detectors and electronics. The power and telemetry requirements on the spacecraft are modest. The majority of mission operations will not be complex, as most observations will be long (~100 ksec), uninterrupted, and pre-planned, although there will be limited capabilities to observe targets of opportunity, such as tidal disruption events or supernovae with a 3-5 day turnaround. After the end of prime science, we plan to allow guest observations to maximize the science return of Arcus to the community.
Arcus is a NASA/MIDEX mission under development in response to the anticipated 2016 call for proposals. It is a freeflying, soft X-ray grating spectrometer with the highest-ever spectral resolution in the 8-51 Å (0.24 – 1.55 keV) energy range. The Arcus bandpass includes the most sensitive tracers of diffuse million-degree gas: spectral lines from O VII and O VIII, H- and He-like lines of C, N, Ne and Mg, and unique density- and temperature-sensitive lines from Si and Fe ions. These capabilities enable an advance in our understanding of the formation and evolution of baryons in the Universe that is unachievable with any other present or planned observatory. The mission will address multiple key questions posed in the Decadal Survey1 and NASA’s 2013 Roadmap2: How do baryons cycle in and out of galaxies? How do black holes and stars influence their surroundings and the cosmic web via feedback? How do stars, circumstellar disks and exoplanet atmospheres form and evolve? Arcus data will answer these questions by leveraging recent developments in off-plane gratings and silicon pore optics to measure X-ray spectra at high resolution from a wide range of sources within and beyond the Milky Way. CCDs with strong Suzaku heritage combined with electronics based on the Swift mission will detect the dispersed X-rays. Arcus will support a broad astrophysical research program, and its superior resolution and sensitivity in soft X-rays will complement the forthcoming Athena calorimeter, which will have comparably high resolution above 2 keV.
NASA's Chandra X-ray Observatory continues to provide an unparalleled means for exploring the high-energy universe. With its half-arcsecond angular resolution, Chandra studies have deepened our understanding of galaxy clusters, active galactic nuclei, galaxies, supernova remnants, neutron stars, black holes, and solar system objects. As we look beyond Chandra, it is clear that comparable or even better angular resolution with greatly increased photon throughput is essential to address ever more demanding science questions—such as the formation and growth of black hole seeds at very high redshifts; the emergence of the first galaxy groups; and details of feedback over a large range of scales from galaxies to galaxy clusters. Recently, we initiated a concept study for such a mission, dubbed X-ray Surveyor. The X-ray Surveyor strawman payload is comprised of a high-resolution mirror assembly and an instrument set, which may include an X-ray microcalorimeter, a high-definition imager, and a dispersive grating spectrometer and its readout. The mirror assembly will consist of highly nested, thin, grazing-incidence mirrors, for which a number of technical approaches are currently under development—including adjustable X-ray optics, differential deposition, and new polishing techniques applied to a variety of substrates. This study benefits from previous studies of large missions carried out over the past two decades and, in most areas, points to mission requirements no more stringent than those of Chandra.
ISS-Lobster is a wide-field X-ray transient detector proposed to be deployed on the International Space Station. Through its unique imaging X-ray optics that allow a 30 deg by 30 deg FoV, a 1 arc min position resolution and a 1.6x10-11 erg/(sec cm2) sensitivity in 2000 sec, ISS-Lobster will observe numerous events per year of X-ray transients related to compact objects, including: tidal disruptions of stars by supermassive black holes, supernova shock breakouts, neutron star bursts and superbursts, high redshift Gamma-Ray Bursts, and perhaps most exciting, X-ray counterparts of gravitational wave detections involving stellar mass and possibly supermassive black holes. The mission includes a 3-axis gimbal system that allows fast Target of Opportunity pointing, and a small gamma-ray burst monitor. In this article we focus on ISS-Lobster measurements of X-ray counterparts of detections by the world-wide ground-based gravitational wave network.
We present the design and scientific motivation for Arcus, an X-ray grating spectrometer mission to be deployed on the International Space Station. This mission will observe structure formation at and beyond the edges of clusters and galaxies, feedback from supermassive black holes, the structure of the interstellar medium and the formation and evolution of stars. The mission requirements will be R>2500 and >600 cm2 of effective area at the crucial O VII and O VIII lines, values similar to the goals of the IXO X-ray Grating Spectrometer. The full bandpass will range from 8-52Å (0.25-1.5 keV), with an overall minimum resolution of 1300 and effective area >150 cm2. We will use the silicon pore optics developed at cosine Research and proposed for ESA’s Athena mission, paired with off-plane gratings being developed at the University of Iowa and combined with MIT/Lincoln Labs CCDs. This mission achieves key science goals of the New Worlds, New Horizons Decadal survey while making effective use of the International Space Station (ISS).
AXSIO’s two focal plane instruments (the imaging X-ray Microcalorimeter Spectrometer and the X-ray Grating
Spectrometer) will deliver a 100-fold increase in capability over the current generation of instruments for high-resolution
spectroscopy, microsecond spectroscopic timing, and high count rate capability. AXSIO covers the 0.1 - 12keV energy
range, complementing the capabilities of the next generation observatories such as ALMA, LSST, JWST, and 30-m
ground-based telescopes These instruments allow AXSIO to accomplish most of the IXO science goals at a significantly
reduced complexity and cost. These capabilities will enable studies of a broad range of scientific questions such as what
happens close to a black hole, how supermassive black holes grow, how large scale structure forms, and what are the
connections between these processes?
Recent advances in X-ray microcalorimeters enable a wide range of possible focal plane designs for the X-ray
Microcalorimeter Spectrometer (XMS) instrument on the future Advanced X-ray Spectroscopic Imaging Observatory
(AXSIO) or X-ray Astrophysics Probe (XAP). Small pixel designs (75 μm) oversample a 5-10″ PSF by a factor of 3-6
for a 10 m focal length, enabling observations at both high count rates and high energy resolution. Pixel designs utilizing
multiple absorbers attached to single transition-edge sensors can extend the focal plane to cover a significantly larger
field of view, albeit at a cost in maximum count rate and energy resolution. Optimizing the science return for a given
cost and/or complexity is therefore a non-trivial calculation that includes consideration of issues such as the mission
science drivers, likely targets, mirror size, and observing efficiency. We present a range of possible designs taking these
factors into account and their impacts on the science return of future large effective-area X-ray spectroscopic missions.
The 2010 Decadal Survey of Astronomy and Astrophysics found the science of the International X-ray Observatory (IXO) compelling, noting that “Large-aperture, time-resolved, high-resolution X-ray spectroscopy is required for future progress on all of these fronts, and this is what IXO can deliver.” In line with Decadal recommendations to reduce cost while maintaining core capabilities, we have developed the Advanced X-ray Spectroscopy and Imaging Observatory (AXSIO). AXSIO reduces IXO's six instruments to two fixed detectors - the imaging X-ray Microcalorimeter Spectrometer and the X-ray Grating Spectrometer. These instruments allow AXSIO to accomplish most of the IXO science goals at a significantly reduced complexity and cost. We present an overview of the AXSIO mission science drivers, its optics and instrumental capabilities, the status of its technology development programs, and the mission implementation approach.
The 2010 Astrophysics Decadal Survey recommended a significant technology development program towards realizing the scientific goals of the International X-ray Observatory (IXO). NASA has undertaken an X-ray mission concepts study to determine alternative approaches to accomplishing IXO’s high ranking scientific objectives over the next decade given the budget realities, which make a flagship mission challenging to implement. The goal of the study is to determine the degree to which missions in various cost ranges from $300M to $2B could fulfill these objectives. The study process involved several steps. NASA released a Request for Information in October 2011, seeking mission concepts and enabling technology ideas from the community. The responses included a total of 14 mission concepts and 13 enabling technologies. NASA also solicited membership for and selected a Community Science Team (CST) to guide the process. A workshop was held in December 2011 in which the mission concepts and technology were presented and discussed. Based on the RFI responses and the workshop, the CST then chose a small group of notional mission concepts, representing a range of cost points, for further study. These notional missions concepts were developed through mission design laboratory activities in early 2012. The results of all these activities were captured in the final Xray mission concepts study report, submitted to NASA in July 2012. In this presentation, we summarize the outcome of the study. We discuss background, methodology, the notional missions, and the conclusions of the study report.
In September 2011 NASA released a Request for Information on “Concepts for the Next NASA X-ray Astronomy
Mission” and formed a Community Science Team to help study the submitted concepts and evaluate their science return
relative to the goals identified by the 2010 Astrophysics Decadal Survey “New Worlds, New Horizons” report. After
reading the responses and participating in a community workshop, the team identified a number of candidate mission
concepts, including one combining advances in large-area precision optics with new X-ray microcalorimeter
technology. However, the exact mission requirements (effective area, field of view, point spread function, etc) were not
fixed. We will present a range of mission designs, describing the results of the NASA/GSFC Mission Design Lab study
of one possible mission along with available deltas that would increase capability or decrease cost.
NuSTAR is a hard X-ray satellite experiment to be launched in 2012. Two optics with 10.15 m focal length focus Xrays
with energies between 5 and 80 keV onto CdZnTe detectors located at the end of a deployable mast. The FM1 and
FM2 flight optics were built at the same time based on the same design and with very similar components, and thus the
performance of both is expected to be very similar. We provide an overview of calibration data that is being used to
build an optics response model for each optic and describe initial results for energies above 10 keV from the ground
calibration of the flight optics. From a preliminary analysis of the data, our current best determination of the overall
HPD of both the FM1 and FM2 flight optics is 52", and nearly independent of energy. The statistical error is negligible,
and a preliminary estimate of the systematic error is of order 4". The as-measured effective area and HPD meet the toplevel
NuSTAR mission sensitivity requirements.
Sensitive surveys of the X-ray universe have been limited to small areas of the sky due to the intrinsically
small field of view of Wolter-I X-ray optics, whose angular resolution degrades with the square of the off axis
angle. High angular resolution is needed to achieve a low background per source, minimize source confusion, and
distinguish point from extended objects. WFXT consists of three co-aligned wide field X-ray telescopes with a
1° field of view and a≲ 10" (goal of 5") angular resolution (HEW) over the full field. Total effective area at 1 keV
will be > 5000 cm2. WFXT will perform three surveys that will cover most of the extragalactic sky to 100-1000
times the sensitivity of the ROSAT All Sky Survey, ≳ 2000 deg2 to deep Chandra or XMM-Newton sensitivity,
and ≳ 100 deg2 to the deepest Chandra sensitivity. WFXT will generate a legacy X-ray data set of ≳ 5 x 105
clusters and groups of galaxies to z ~ 2, also characterizing the physics of the intracluster gas for a significant
fraction of them, thus providing an unprecedented data set for cosmological applications; it will detect > 107
AGN to z > 6, again obtaining spectra for a substantial fraction; it will detect > 105 normal/starburst galaxies;
and it will detect and characterize star formation regions across the Galaxy. WFXT is the only X-ray survey
mission that will match, in area and sensitivity, the next generation of wide-area optical, IR and radio surveys.
The Wide Field X-Ray Telescope (WFXT) will carry out an unprecedented X-ray survey of galaxy clusters and groups, AGNs and QSOs, and galaxies. WFXT is a medium-class strategic mission that will address key questions in both Cosmic Origins and Physics of the Cosmos. WFXT will be orders of magnitude more effective than previous X-ray missions in performing surveys to a given limiting flux. The angular resolution of ~5" will be finer than provided by any currently planned large-area X-ray survey and highly efficient at discriminating AGNs and QSOs from extended emission from sources such as galaxies and clusters. The Burrows, Burg and Giacconi ideal optical solution gives an approximately constant angular resolution of 3-5 arc seconds across a field of 1-1.5 degrees diameter. A preliminary telescope design provides a resulting grasp an order of magnitude larger than current or future missions. We plan a combination of three surveys and, at each flux limit, WFXT will cover orders of magnitude more area than all previous and planned missions, with the deep 100 deg2 survey reaching the same flux limit as the deepest Chandra surveys to date. The WFXT mission addresses key cosmological and astrophysical science objectives including: the formation and evolution of clusters of galaxies with the associated cosmological and astrophysical implications; black hole formation and evolution; the interaction of black-hole driven AGNs with cluster and galaxy properties; and the high-energy stellar component and the hot ISM phase of galaxies WFXT is a mission for the entire astronomical community. The data from these surveys will be made readily available to the community in timely data releases to be used in a multitude of multi-waveband studies that will revolutionize astronomy.