3,550 research outputs found
Beyond Chandra - the X-ray Surveyor
Over the past 16 years, NASA's Chandra X-ray Observatory has provided an
unparalleled means for exploring the universe with its half-arcsecond angular
resolution. Chandra studies have deepened our understanding of galaxy clusters,
active galactic nuclei, galaxies, supernova remnants, planets, and solar system
objects addressing almost all areas of current interest in astronomy and
astrophysics. As we look beyond Chandra, it is clear that comparable or even
better angular resolution with greatly increased photon throughput is essential
to address even more demanding science questions, such as the formation and
subsequent growth of black hole seeds at very high redshift; the emergence of
the first galaxy groups; and details of feedback over a large range of scales
from galaxies to galaxy clusters. Recently, NASA Marshall Space Flight Center,
together with the Smithsonian Astrophysical Observatory, has initiated a
concept study for such a mission named the X-ray Surveyor. This study starts
with a baseline payload consisting of a high resolution X-ray telescope and an
instrument set which may include an X-ray calorimeter, a wide-field imager and
a dispersive grating spectrometer and readout. The telescope would consist of
highly nested thin shells, for which a number of technical approaches are
currently under development, including adjustable X-ray optics, differential
deposition, and modern polishing techniques applied to a variety of substrates.
In many areas, the mission requirements would be no more stringent than those
of Chandra, and the study takes advantage of similar studies for other large
area missions carried out over the past two decades. Initial assessments
indicate that such an X-ray mission is scientifically compelling, technically
feasible, and worthy of a high rioritization by the next American National
Academy of Sciences Decadal Survey for Astronomy and Astrophysics.Comment: 6 pages, 6 figures, paper 9510-01 presented at SPIE Europe, Prague,
April 201
Exploring the NRO Opportunity for a Hubble-sized Wide-field Near-IR Space Telescope -- NEW WFIRST
We discuss scientific, technical and programmatic issues related to the use
of an NRO 2.4m telescope for the WFIRST initiative of the 2010 Decadal Survey.
We show that this implementation of WFIRST, which we call "NEW WFIRST," would
achieve the goals of the NWNH Decadal Survey for the WFIRST core programs of
Dark Energy and Microlensing Planet Finding, with the crucial benefit of deeper
and/or wider near-IR surveys for GO science and a potentially Hubble-like Guest
Observer program. NEW WFIRST could also include a coronagraphic imager for
direct detection of dust disks and planets around neighboring stars, a
high-priority science and technology precursor for future ambitious programs to
image Earth-like planets around neighboring stars.Comment: 76 pages, 26 figures -- associated with the Princeton "New Telescope
Meeting
Radial Velocity Prospects Current and Future: A White Paper Report prepared by the Study Analysis Group 8 for the Exoplanet Program Analysis Group (ExoPAG)
[Abridged] The Study Analysis Group 8 of the NASA Exoplanet Analysis Group
was convened to assess the current capabilities and the future potential of the
precise radial velocity (PRV) method to advance the NASA goal to "search for
planetary bodies and Earth-like planets in orbit around other stars.: (U.S.
National Space Policy, June 28, 2010). PRVs complement other exoplanet
detection methods, for example offering a direct path to obtaining the bulk
density and thus the structure and composition of transiting exoplanets. Our
analysis builds upon previous community input, including the ExoPlanet
Community Report chapter on radial velocities in 2008, the 2010 Decadal Survey
of Astronomy, the Penn State Precise Radial Velocities Workshop response to the
Decadal Survey in 2010, and the NSF Portfolio Review in 2012. The
radial-velocity detection of exoplanets is strongly endorsed by both the Astro
2010 Decadal Survey "New Worlds, New Horizons" and the NSF Portfolio Review,
and the community has recommended robust investment in PRVs. The demands on
telescope time for the above mission support, especially for systems of small
planets, will exceed the number of nights available using instruments now in
operation by a factor of at least several for TESS alone. Pushing down towards
true Earth twins will require more photons (i.e. larger telescopes), more
stable spectrographs than are currently available, better calibration, and
better correction for stellar jitter. We outline four hypothetical situations
for PRV work necessary to meet NASA mission exoplanet science objectives.Comment: ExoPAG SAG 8 final report, 112 pages, fixed author name onl
Lynx X-Ray Observatory: An Overview
Lynx, one of the four strategic mission concepts under study for the 2020 Astrophysics Decadal Survey, provides leaps in capability over previous and planned x-ray missions and provides synergistic observations in the 2030s to a multitude of space- and ground-based observatories across all wavelengths. Lynx provides orders of magnitude improvement in sensitivity, on-axis subarcsecond imaging with arcsecond angular resolution over a large field of view, and high-resolution spectroscopy for point-like and extended sources in the 0.2- to 10-keV range. The Lynx architecture enables a broad range of unique and compelling science to be carried out mainly through a General Observer Program. This program is envisioned to include detecting the very first seed black holes, revealing the high-energy drivers of galaxy formation and evolution, and characterizing the mechanisms that govern stellar evolution and stellar ecosystems. The Lynx optics and science instruments are carefully designed to optimize the science capability and, when combined, form an exciting architecture that utilizes relatively mature technologies for a cost that is compatible with the projected NASA Astrophysics budget
Modern Aerocapture Guidance to Enable Reduced-Lift Vehicles at Neptune
Aerocapture is covered extensively in the literature as means of achieving orbital insertion with dramatic mass-saving results compared to fully-propulsive systems. One of the primary obstacles facing aerocapture is the inherent uncertainty associated with passing through a planets upper atmosphere. In-flight dispersions due to delivery errors, environment variables, and aerodynamic performance impose a large flight envelope. System studies for aerocapture often select high lift-to-drag ratios to compensate for these uncertainties. However, modern predictor-corrector guidance strategies have shown promise in recent years to provide robust control schemes in-situ. These algorithms do not rely on a pre-calculated reference trajectory and instead employ a numerical optimizer to continuously solve nonlinear equations of motion each guidance cycle. Numerical predictor-corrector strategies may provide considerable accuracy over heritage guidance schemes. The goal of this study is reproduce a landmark study of Neptune aerocapture and apply modern guidance to illustrate relative performance improvements and cost-saving potential. Capture constraints based on the theoretical corridor width are considered. Results indicate that heritage vehicles with moderate lift-to-drag ratios, lower than previous studies have indicated, may prove viable for aerocapture at Neptune
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