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New Worlds, New Horizons in Astronomy and Astrophysics D Mid-Scale Project Descriptions This survey received 29 proposals that would be eligible for competition, with an aggregate construction or fabrication cost of roughly $1.2 billion. The Program Prioritization Panels recommended a subset of these very highly, at a rough total cost of $400 million. It is not appropriate for this survey to make priority assessments for activities that would compete in a peer-reviewed program. However, the case for such a program line is best made by describing selected examples, as is done below in alphabetical order and in Table 7.1. Not all of them will be funded, but the funding recommended would be sufficient to proceed with many of them, as well as several excellent new proposals that will surely be submitted in response to a general solicitation. These proposals are grouped into three cost categories based on submitted descriptions and not an independent committee review. It is important that the Mid-Scale Innovations Program itself maintain a balance between large and small projects. $40 MILLION TO $120 MILLION RANGE Big Baryon Oscillation Spectroscopic Survey. The Big Baryon Oscillation Spectroscopic Survey (BigBOSS) would utilize the Kitt Peak National Observatory 4-meter Mayall telescope and a newly built optical spectrograph capable of measuring more than 5,000 spectra simultaneously over a 3-degree field of view. The science goal is understanding the acceleration of the universe by observing the distributions of 30 million galaxies and a million quasars. These data will also address important
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New Worlds, New Horizons in Astronomy and Astrophysics questions concerning the formation and evolution of galaxies, black holes, and the intergalactic medium. Frequency Agile Solar Radiotelescope. The Frequency Agile Solar Radiotelescope (FASR) consists of three arrays of radio telescopes operating across a broad range of frequency (from 50 megahertz to 20 gigahertz). Its overall scientific program is to conduct time-domain mapping of the solar atmosphere in a campaign mode, delivering data products to the solar physics community. These will be used to study the nature and evolution of the Sun’s magnetic field, to understand solar flares, improve the ability to predict “space weather” caused by solar activity, and better understand the quiet sun. Hydrogen Epoch of Reionization Array. The Hydrogen Epoch of Reionization Array (HERA) is a multistage project in radio astronomy to understand how hydrogen is ionized after the first stars start to shine. The first phase (HERA I) is under way and will demonstrate the feasibility of the technical approach. The second phase (HERA II) would serve as a pathfinder for an eventual worldwide effort in the following decade to construct a facility with a total collecting area of a square kilometer and the power to make detailed maps of this critical epoch in the history of the universe. Proceeding with HERA II should be subject to HERA I meeting stringent performance requirements in its ability to achieve system calibration and the removal of cosmic foreground emission. North American Nanohertz Observatory for Gravitational Waves. The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) would utilize the naturally occurring population of precision astronomical “clocks” called pulsars (rapidly spinning neutron stars) to detect very low frequency gravitational waves using upgraded capabilities of the existing Arecibo and Robert Byrd radio telescopes. The pulsar timing should also be able to detect the formation and collision of massive black holes with signals at periods of months to several years. This facility might even be able to detect relic gravitational waves from the very early universe (which is otherwise inaccessible to direct observations). $12 MILLION TO $40 MILLION RANGE Cosmic Microwave Background Initiatives. NSF has invested wisely in the past in ground-based telescopes that have considerably advanced the understanding of the fluctuations, polarization, and distortion of the cosmic microwave background through the Sunyaev-Zeldovich effect and gravitational lensing in a way that has complemented the suborbital and space program especially by working at smaller angular scales. Thanks to the development of new detector technology, ground-
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New Worlds, New Horizons in Astronomy and Astrophysics based observations are likely to remain highly competitive over the coming decade. The largest challenge to these observations is to detect the B-mode polarization that may be associated with very long wavelength gravitational radiation that was set down during the epoch of inflation. Exoplanet Initiatives. The discovery and the study of exoplanets are developing at an extraordinarily rapid pace. It will be important to make strategic investments in new ground-based capabilities during the coming decade. One important component will be the aggressive development of ground-based high-precision radial velocity surveys of nearby stars at optical and near-infrared wavelengths (including efforts to determine the effects of stellar activity on these measurements). These surveys will need new spectrometers and significant time allocation on 8- to 10-meter-class telescopes. Another possibility is the development of ground-based high-spatial-resolution techniques in an exoplanet context for direct and indirect detection, and a third, facilities dedicated to surveying exozodiacal dust around nearby stars from the ground. Next-Generation Adaptive Optics Systems. The adaptive optics technique can correct the distortions that are introduced by turbulence in Earth’s atmosphere in images taken with ground-based telescopes. This technique enables near-infrared images to be obtained with resolution superior to that provided by the Hubble Space Telescope. The next generation of such systems deployed on the existing 8- to 10-meter telescopes will offer major improvements in the quality and wavelength coverage of the images, and in the fraction of the sky accessible to adaptive optics. Next-Generation Instruments for Solar Telescopes. The Advanced Technology Solar Telescope (ATST) is currently in the MREFC construction queue. The Mid-Scale Innovations Program would be one avenue for providing a second generation of instruments for this facility and maintaining its cutting-edge capabilities. $4 MILLION TO $12 MILLION RANGE High Altitude Water Čerenkov Experiment. The High Altitude Water Čerenkov experiment (HAWC), sited in Mexico, is proposed to map the sky at gamma-ray energies above 1 TeV and detect transient sources. With its very large field of view, it will complement the proposed atmospheric Čerenkov facility.
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