The Role of Interferometers in Future Space Astrophysics Missions
Ron Allen (STScI)
An important aspect of future space astrophysics missions in the UV-O-IR range is the pursuit of higher angular resolution. Such missions include the characterisation of exoplanetary systems, and imaging the surfaces of stars. Some of the general features of interferometeric imaging systems are discussed here, including their advantages and disadvantages. The physics of image formation and restoration using interferometers is well understood from radio astronomy, and a number of ground-based systems have shown that this experience is directly applicable to the UV-optical-IR systems we hope to see in space. The challenges presently are in the engineering. The lack of a coherent technical program to address these challenges within NASA, the astronomy community, and Industry. is a major concern for the future.
The Future of Direct Supermassive Black Hole Mass Measurements
The existence of supermassive black holes (SMBHs) at the centers of galactic bulges has now been supposed for many decades. However, there are only a few cases in which the masses of the SMBHs have been directly measured with such accuracy as to categorically rule out all other possibilities. Due to the observed correlations between SMBH mass estimates and the more general bulge properties, generating a sample of reliable SMBH masses is critical for not only understanding their formation and evolution, but also the formation and evolution of galaxies themselves. We will review the status, and limitations, of SMBH mass estimates made to date, before discussing the observations required to make reliable SMBH mass measurements using current techniques. Finally, we will assess the ability of future missions to deliver the data necessary to constrain some of the most fundamental questions remaining in contemporary astrophysics.
Remote Sensing for Space Exploration in 50 Years
Several important problems in astronomy require wavefront capture and control over large distances to improve angular resolution and light sensitivity. Two of the most compelling are the search for signatures of life in extra-solar planetary systems and the study of black holes near their event horizons, but a host of other topics including the study of stars, the Solar System, and whole-Earth monitoring would be qualitatively changed by the use of very large telescopes and interferometers in space. These telescopes would expand our ability to carry out space exploration through remote sensing by an enormous factor and would be cost effective compared to in situ measurements.
They should be an important third prong of the Vision for Space Exploration alongside robot and human visitation of the Moon and other planets.
Multiple Spacecraft Observatories for 2020 and Beyond: Breaking a Tradition of Four Centuries
Since the time of Galileo, a telescope has been an optic, physically coupled to a detector, pointed at a target. As astronomers ventured into space they largely carried this paradigm with them, building ever more powerful and sophisticated telescopes. But as radio astronomers discovered in the 1950, there comes a time when multiple units must be coupled together in new and innovative ways. I will discuss the impact of formation flying on the next generation of space observatories. Missions such as LISA, New Worlds Observer, MAXIM, SPECS, Stellar Imager and TPF-I are already laying the groundwork for what may become a permanent change in the nature of space observatories.
20/20 Vision: The Technology, the Facilities, the Science and the Politics That May Drive Space Astrophysics Observatories in the 21st Century
Jim Crocker (Lockheed Martin)
Abstract to be submitted
Technologies for Astrophysics Missions in 2020
Dennis Ebbets (Ball Aerospace)
Space missions being developed in this decade are pioneering many technological innovations that will be mature and available to enable astrophysics missions next decade. I will cite examples from missions that my company, Ball Aerospace & Technologies Corp., has been involved with. Examples include the deployment and control of segmented optical systems to overcome limitations of launch vehicle fairings, large focal plane arrays for wide fields of view, cryogenic systems for cooling detectors and optical systems, and optical communications to allow very high data transmission rates. Other capabilities that have or will be demonstrated shortly include coordinated operation of multiple spacecraft, sensors and algorithms for proximity operations, and technologies for robotic servicing of observatories in space. Most of these would be applicable to a wide range of mission sizes, from Explorers to Great Observatories.
Future Giant Telescopes: Evolution in Ground-Space Synergy
The widespread realization of laser-guide star adaptive optics is changing the oft-quoted synergy established in the 1990's between our ground- based telescopes and Hubble. Future AO-based facilities such as the Thirty Meter Telescope will have a better angular resolution and light grasp than JWST leading to a new partnership between ground and space. I will explore how this progress could redirect the needs of future space missions operating at UV through infrared wavelengths.
High Resolution X-ray Imaging after Chandra: The Generation-X Mission Concept
The sub-arcsecond imaging of Chandra has revolutionized X-ray astronomy and has had a great impact on astrophysics as a whole. With Chandra's angular resolution we can see far fainter sources leading to quantitative leaps in source numbers in e.g. star formation regions, galaxies and deep surveys, we can see qualitatively new structures in extended sources such as supernova remnants and clusters of galaxies showing us obvious signs of feedback from AGNs to cluster 'cool cores', and has extended singular objects into new classes of X-ray source, with the pulsar wind nebulae being a striking example.
A larger, high angular resolution, successor to Chandra will certainly be needed. Already the typical exposure time is nearly 1 day long, reflecting the small effective area Chandra supplies <1000cm^2. The challenge of making sub-arcsecond grazing incidence X-ray mirrors with far larger area than Chandra's, at reasonable cost, is daunting, and the planned new generation of X-ray missions contains nothing that approaches these properties.
This lack creates a yawning gap in future of astrophysics. X-rays give one of the few windows to observing the first stars, galaxies and black holes at z~10-20 and unique insights into extreme environments throughout the universe.
While the powerful spectroscopy of Con-X addresses important classes of these environments, others require Chandra-like or better X-ray imaging.
We have been working to fill this gap. Using the lightweight Con-X mirrors as a starting point, we plan to combine them with active X-ray optics techniques now employed at synchrotrons world-wide to design an X-ray mission with 0.1 arcsecond HPD, and an area up to 100 square meters. This is Generation-X.
Astrophysics Missions in ESA's Cosmic Vision 2015-2025 Program
Fabio Favata (ESA)
Abstract to be submitted
Enhancing the Characterization of Extrasolar Planets via Direct Detection with a Coronagraphic Terrestrial Planet Finder
The direct detection of extrasolar planet will enable the characterization of planet's physical properties. Such research will provide valuable context for interpreting the physical properties of planets in our own solar system. While extreme adaptive optics at large ground-based observatories and intermediate-scale space missions may be capable of directly detecting some giant planets, large spaced-based observatories appear to offer the best prospects for directly detecting and characterizing distant Earth-like planets. Previous designs for Terrestrial Planet Finder missions were constrained by the physical size of currently available launch vehicles. Should larger launch vehicles become available, the design of large space missions optimized for planet characterization should be revisited. Clearly, a larger collecting area would reduce the integration times needed to search for terrestrial mass planets and increase the practical temporal/spectral resolution of observations performing follow-up characterization. In this talk, I will outline several additional benefits. For example, a larger aperture would allow for surveys of a larger number of stellar/planet targets, both because of the increased collecting area and the reduced inner working angle.
Thus, planets in the habitable zones of more distant stars and more nearby sub-solar-mass stars could become accessible. Further, when operated in detection mode, the number of epochs needed to obtain a significant null detection would be significantly reduced. As another example, a larger aperture could enable near infrared observations of planets in the habitable zone of a modest number of nearby stars, even with a monolithic observatory. If combined with appropriate instrumentation, increasing the aperture to allow for observations extending to two microns could enable searches for several new absorption bands, including those due to water, carbon dioxide, methane, and perhaps even ammonia. Such extended spectral range could provide valuable information that would greatly aid the spectroscopic characterization of terrestrial planets, particularly given the relatively low spectral resolution and signal to noise that are inevitable for such challenging observations.
The Importance of High Spatial and Appropriate Spectral Resolution Spectroscopy
Many diverse astronomical sources are resolved with diffraction-limited large telescopes. Application of appropriate dispersion spectroscopy unveils much information on the physics of these objects ranging from gamma ray bursters in host galaxies, star-formation regions and central engines in nearby galaxies, structures in galactic nebulae, resolved binaries with mass exchange, extended winds of massive stars, protoplanetary systems, and comets, asteroids and planets within our own solar system. Active optics and interferometers coupled with spectrographs can provide near-diffraction-limited spectroscopy from the ground but only longward of one micron. Below one micron, and certainly below 6000A, we must turn to space-based large telescopes equipped with spectrographs capable of providing spatially diffraction-limited spectroscopy of astronomical sources. Examples will be presented from the HST/STIS, ground-based and other instruments on science that has been accomplished. Suggestions will be made of what might be possible, and limitations thereof, with future large monolithic, multiple mirror or interferometric telescopes equipped with spectrographs that would be matched to the diffraction limit of the telescope.
Massively Parallel Ground-Based Follow-Up by Amateur and Educational Communities Beyond the Next Decade
Computer vision and geometric hashing techniques from computer science have made possible automated data analysis, archiving, search, and retrieval among highly heterogeneous and badly archived data sets. We have shown that we can solve the totally "blind astrometry" problem (determine precise image pointing and field of view using *nothing* but the information in the image pixels) for a wide range of astronomical images, quickly and robustly. This blind system brings all of the data in digitized plate archives, amateur basements, online photo-sharing sites, and educational-observatory computers into the professional domain for research and discovery. In the coming decade, it will also generate enormous amounts of knowledge about amateur and educational-observatory capabilities (both the hardware and the personnel), reward the competent with involvement in research activity, and create two-way communications among the research, educational, and amateur communities. One long-term goal is to organize these communities into an "always-up" rapid response system, with heterogeneously taken but uniformly processed, calibrated, and archived data. Such a system would have a large impact on the context of space missions beyond the next decade.
Mapping the Structure of All Matter in the Universe
Abstract to be submitted
Far-IR Space Interferometry: Science Opportunities, Mission Concepts and Technical Challenges
Sensitive far-IR imaging and spectroscopic measurements of astronomical objects on sub-arcsecond angular scales are essential to our understanding of star and planet formation, the formation and evolution of galaxies, and to the detection and characterization of extrasolar planets. Cold single-aperture telescopes in space, such as the Spitzer Space Telescope and the Herschel Space Observatory, are very sensitive, but they lack the necessary angular resolution by two or more orders of magnitude. Far-IR space interferometers will address this need in the coming decades. Several mission concepts have already been studied, including in the US the Space Infrared Interferometric Telescope (SPIRIT) and the more ambitious Submillimeter Probe of the Evolution of Cosmic Structure (SPECS), and a Far-IR Interferometer (FIRI) was recently proposed to ESA under the Cosmic Vision program. This talk will describe science goals and summarize alternative concepts for future far-IR space interferometry missions. The technology requirements for far-IR interferometry will also be discussed.
Technology Responsivity and Risk Mitigation: Optimizing the Programmatic S/N of Future Large Space Telescopes
Abstract to be submitted
Extrasolar Planets : The Landscape in 2020
Abstract to be submitted
Detection of relic gravitational waves and rotation of the Universe by direct angular measurements at 1 microarcsecond
Valeri Makarov (Michelson Science Center, Caltech)
The origin of the Universe and the circumstances of its initial evolution are imprinted in the pattern of the motion of very distant quasars and the metric of spacetime on cosmological scales. In particular, the theoretically postulated relic gravitational waves from the Big Bang epoch cause the light rays from distant quasars to bend in a systematic, predictable pattern, which is measurable at the microarcsecond level as a global field of angular velocities. Dynamical perturbations at the epoch of reionization can lead to differential vorticity fields of observable matter, which are detected as second- and higher order magnetic vector harmonics of the global velocity field. A concept of a dedicated astrometric (or rather, cosmometric) telescope is presented deemed capable of taking measurements of relatively faint (17 - 18 mag) optical sources in a global grid to the required accuracy. The astrophysical agenda for his facility is rich besides the primary goals, including such topics as direct measurement of the gravitational potential of dark matter in the Milky Way and nearby galaxies haloes, internal kinematics of globular clusters, the search for a dark companion to the Sun (the Nemesis problem), and detection of planets orbiting dim stars.
The 20/20 Vision of Galaxy Formation and Reionization
Sangeeta Malhotra (Arizona State University)
While galaxy formation is a continuous process, there is an urge to determine the moment in time where the 'dark ages' ended. This is done by determining the epoch of reionization, when hydrogen in the inter-galactic medium was ionized. This implies that enough star-formation had happened to produce several ultraviolet photons for each hydrogen atom. Whether this phase transition was quick or slow, and patchy or simultaneous across large swaths of space, will tell us a lot about galaxy and star formation in the first billion years. Observational studies of the earliest galaxies as initiators and probes of reionization have had many recent successes, but we lack (1) good, statistical samples and (2) knowledge of the physical nature of these galaxies.
Some of this can be addressed by JWST and large ground-based telescopes like ALMA and TMT/ELT/GSMT. The most interesting question for this meeting is: which of these challenges would be unmet by currently planned missions?
Enabling Future Large Space Astrophysics Missions While Living Within Our Means
Abstract to be submitted
Large Deployed and Assembled Space Telescopes
Ron Polidan (Northrop Grumman Space Technology)
Abstract to be submitted
Gravitational Wave Astronomy from Space
Thomas Prince (Caltech)
Gravitational wave astronomy will be a new way of observing the universe and has tremendous potential for providing unique information on important questions in physics and astrophysics. I will first review the principles that make gravitational wave observations such a unique and important tool for astronomy. I will then discuss specific projects and missions, with particular emphasis on the Laser Interferometer Space Antenna (LISA), a joint ESA-NASA space mission. To finish, I will briefly speculate on possible missions that may come after LISA, such as the Big Bang Observer (BBO).
Cracking the Mystery of Galaxy and Black Hole Formation: A Theorists' Wish-List for the Next Generation of Space Telescopes
Abstract to be submitted
The Next Large X-ray Mission - Constellation-X
The Constellation X-ray Mission will open a new window on x-ray spectroscopy. Integrated over the 0.6-10 keV energy band, Constellation-X will have 100 times the throughput of the gratings aboard Chandra and XMM-Newton. The Constellation-X resolving power will exceed 1250 from 0.3-1.0 keV and 2400 at6 keV. A hard x-ray telescope will extend the bandpass of Constellation-X upwards to at least 40 keV. Constellation-X will probe the physics of extreme processes, events, and systems - where high temperatures, intense gravity, strong magnetic fields and the like produce x-ray radiation.
This talk will present an overview of the mission configuration and the key scientific components. The presentation will describe the breadth of anticipated science such as: measurements of iron lines near event horizons to determine black hole spin and test predictions of general relativity, measurements of turbulence in clusters of galaxies via broadening of iron lines to determine the non-thermal energy content of the clusters, determination of mass and radius for neutron stars with x-ray bursts to limit possible equations of state for ultra-dense matter, measurement of production of heavy elements from carbon to zinc in supernova explosions, measurement of highly ionized oxygen in the warm interstellar medium, and studies of stellar coronae via x-ray Doppler imaging.
Imaging Inflation with Cosmic Microwave Background Polarization
One of the most spectacular scientific breakthroughs in past decades was using measurements of the fluctuations in the cosmic microwave background (CMB) to test precisely our understanding of the history and composition of the Universe. I describe what I view as the logical next step for CMB research: using precision polarization measurements to learn about ultra-high-energy physics and the Big Bang itself.
Resolved Stellar Populations Beyond the Next Decade
Abstract to be submitted
Exoplanet Science with Ares-V Enabled Telescopes
Direct detection of exoplanets has a huge potential ability to tell us about relatively detailed conditions on those planets, including the search for life on an Earth-like terrestrial one. This potential is limited by a number of instrumental realities, among which the hardest to overcome are the faintness of exoplanets and the background photons from the exozodi dust disk within which the exoplanets are likely to be orbiting.
The Ares V can provide a means to the solution for both of these limiting factors. For any of the presently contemplated versions of the Terrestrial Planet Finder missions, whether internal coronagraph, external coronagraph (occulter), or interferometer with free-flying spacecraft, the main performance limitations are collecting area and angular resolution. These two factors are directly related to the constraints of faintness and exozodi: larger collecting areas increase the signal counts, and large baselines increase the angular resolution hence the separation of planet from background.
In this talk I will focus on the dramatically large scientific improvement expected in the characterization of an exoplanet from the capabilities to be provided by the Ares V launch vehicle.
The Dark Ages Lunar Interferometer (DALI)
The Dark Ages Lunar Interferometer (DALI) is a Moon-based radio telescope concept aimed at imaging highly-redshifted neutral hydrogen signals from the first large scale structures forming during the Universe’s “Dark Ages” and “Epoch of Reionization.” The Universe’s Dark Ages consist of the interval after recombination until the formation of the first luminous objects, when the Universe was unlit by any stars. During the Dark Ages, baryons -- neutral hydrogen atoms -- were able to collapse into dark matter-dominated, overdense regions. As the H I gas accumulated in overdense regions, its excitation temperature decoupled from, and became lower than, the temperature of the cosmic microwave background (CMB). Observations of the highly-redshifted hyper?ne (21-cm) transition should show a patchwork of absorption features from the first large-scale structures against the CMB. Observing these features would probe structure formation in the relatively simple linear regime, and the H I line may represent the only means of obtaining information about this cosmic epoch. Later, at redshifts z ~ 10, the first stars and black holes formed in these overdense regions, and their collective UV radiation led to the Universe becoming nearly fully ionized, a state in which it remains today. The Epoch of Reionization (EoR) marks this second transition, during which time the 21-cm line excitation temperature should have risen, eventually exceeding the CMB temperature, until essentially all of the hydrogen was ionized. Imaging the (redshifted) 21-cm line of H I at different wavelengths will construct a tomographic or 3-dimensional view of the Dark Ages and EoR. Operating at 1 - 30 meter wavelengths (10 - 300 MHz), probing redshifts 6 < z < 100, DALI would be located on the far side of the Moon, where it would be shielded from terrestrial emissions and, for half of the Moon’s orbit, from solar radio emissions. In order to have sufficient sensitivity, the array must have an effective collecting area of at least 10 km^2 (10^7 m^2). As a secondary science goal, DALI will target auroral radio bursts from extrasolar planets in order to study their magnetospheres, potentially helping to distinguish habitable and non-habitable terrestrial-mass planets in the solar neighborhood. We illustrate the notional DALI concept and identify areas of technology development that will be required over the next decade that would allow the deployment of DALI in following decades.