187 research outputs found
Advanced X-ray Astrophysics Facility (AXAF): An overview
The Advanced X-ray Astrophysics Facility (AXAF) is the x-ray component of NASA's Great Observatories. To be launched in late 1998, AXAF will provide unprecedented capabilities for high-resolution imaging, spectrometric imaging, and high-resolution disperse spectroscopy, over the x-ray band from about 0.1 keV to 10 keV. With these capabilities, AXAF observations will address many of the outstanding questions in astronomy, astrophysics, and cosmology
UV and EUV Instruments
We describe telescopes and instruments that were developed and used for
astronomical research in the ultraviolet (UV) and extreme ultraviolet (EUV)
regions of the electromagnetic spectrum. The wavelength ranges covered by these
bands are not uniquely defined. We use the following convention here: The EUV
and UV span the regions ~100-912 and 912-3000 Angstroem respectively. The
limitation between both ranges is a natural choice, because the hydrogen Lyman
absorption edge is located at 912 Angstroem. At smaller wavelengths,
astronomical sources are strongly absorbed by the interstellar medium. It also
marks a technical limit, because telescopes and instruments are of different
design. In the EUV range, the technology is strongly related to that utilized
in X-ray astronomy, while in the UV range the instruments in many cases have
their roots in optical astronomy. We will, therefore, describe the UV and EUV
instruments in appropriate conciseness and refer to the respective chapters of
this volume for more technical details.Comment: To appear in: Landolt-Boernstein, New Series VI/4A, Astronomy,
Astrophysics, and Cosmology; Instruments and Methods, ed. J.E. Truemper,
Springer-Verlag, Berlin, 201
Localizing Gravitational Wave Sources with Single-Baseline Atom Interferometers
Localizing sources on the sky is crucial for realizing the full potential of
gravitational waves for astronomy, astrophysics, and cosmology. We show that
the mid-frequency band, roughly 0.03 to 10 Hz, has significant potential for
angular localization. The angular location is measured through the changing
Doppler shift as the detector orbits the Sun. This band maximizes the effect
since these are the highest frequencies in which sources live several months.
Atom interferometer detectors can observe in the mid-frequency band, and even
with just a single baseline can exploit this effect for sensitive angular
localization. The single baseline orbits around the Earth and the Sun, causing
it to reorient and change position significantly during the lifetime of the
source, and making it similar to having multiple baselines/detectors. For
example, atomic detectors could predict the location of upcoming black hole or
neutron star merger events with sufficient accuracy to allow optical and other
electromagnetic telescopes to observe these events simultaneously. Thus,
mid-band atomic detectors are complementary to other gravitational wave
detectors and will help complete the observation of a broad range of the
gravitational spectrum.Comment: 16 pages, 3 figures, 2 table
Preliminary scientific rationale for a voyage to a thousand astronomical units
A proposed mission to 1000 astronomical units (TAU) is under study by the Jet Propulsion Laboratory. Launch date for a TAU mission is likely to be well into the first decade of the 21st century. Study of TAU has focused on the technologies required to carry out this ambitious mission and the identification of preliminary scientific rationale for such a deep space flight. A 1-MW nuclear-powered electric propulsion (NEP) system forms the baseline method for achieving the high velocities required. A solar system escape velocity of 106 km/s is needed to propel the TAU vehicle to 1000 AU in 50 years. The NEP system must accelerate the vehicle for about ten years before this velocity is attained because of the extremely low thrust nature of the xenon-fueled ion engines. At the end of the thrusting phase the NEP system is jettisoned to allow the TAU spacecraft and science experiments to coast out to 1000 AU. Another important technology for TAU is advanced optical communication systems, which are envisioned for transmitting science data to Earth. A 1-m optical telescope combined with a 10-W laser transponder can transmit 20 kbps to a 10-m Earth-orbit-based telescope from 1000 AU
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