2,644 research outputs found
CIS-lunar space infrastructure lunar technologies: Executive summary
Technologies necessary for the creation of a cis-Lunar infrastructure, namely: (1) automation and robotics; (2) life support systems; (3) fluid management; (4) propulsion; and (5) rotating technologies, are explored. The technological focal point is on the development of automated and robotic systems for the implementation of a Lunar Oasis produced by Automation and Robotics (LOAR). Under direction from the NASA Office of Exploration, automation and robotics were extensively utilized as an initiating stage in the return to the Moon. A pair of autonomous rovers, modular in design and built from interchangeable and specialized components, is proposed. Utilizing a buddy system, these rovers will be able to support each other and to enhance their individual capabilities. One rover primarily explores and maps while the second rover tests the feasibility of various materials-processing techniques. The automated missions emphasize availability and potential uses of Lunar resources, and the deployment and operations of the LOAR program. An experimental bio-volume is put into place as the precursor to a Lunar environmentally controlled life support system. The bio-volume will determine the reproduction, growth and production characteristics of various life forms housed on the Lunar surface. Physicochemical regenerative technologies and stored resources will be used to buffer biological disturbances of the bio-volume environment. The in situ Lunar resources will be both tested and used within this bio-volume. Second phase development on the Lunar surface calls for manned operations. Repairs and re-configuration of the initial framework will ensue. An autonomously-initiated manned Lunar oasis can become an essential component of the United States space program
The Magellanic System: What have we learnt from FUSE?
I review some of the findings on the Magellanic System produced by the Far
Ultraviolet Spectroscopic Explorer (FUSE) during and after its eight years of
service. The Magellanic System with its high-velocity complexes provides a
nearby laboratory that can be used to characterize phenomena that involve
interaction between galaxies, infall and outflow of gas and metals in galaxies.
These processes are crucial for understanding the evolution of galaxies and the
intergalactic medium. Among the FUSE successes I highlight are the coronal gas
about the LMC and SMC, and beyond in the Stream, the outflows from these
galaxies, the discovery of molecules in the diffuse gas of the Stream and the
Bridge, an extremely sub-solar and sub-SMC metallicity of the Bridge, and a
high-velocity complex between the Milky Way and the Clouds.Comment: A contributed paper to the FUSE Annapolis Conference "Future
Directions in Ultraviolet Spectroscopy.", 5 pages. To appear as an AIP
Conference Proceedin
Tracking The Post-BBN Evolution Of Deuterium
The primordial abundance of deuterium produced during Big Bang
Nucleosynthesis (BBN) depends sensitively on the universal ratio of baryons to
photons, an important cosmological parameter probed independently by the Cosmic
Microwave Background (CMB) radiation. Observations of deuterium in
high-redshift, low-metallicity QSO Absorption Line Systems (QSOALS) provide a
key baryometer, determining the baryon abundance at the time of BBN to a
precision of 5%. Alternatively, if the CMB-determined baryon to photon ratio is
used in the BBN calculation of the primordial abundances, the BBN-predicted
deuterium abundance may be compared with the primordial value inferred from the
QSOALS, testing the standard cosmological model. In the post-BBN universe, as
gas is cycled through stars, deuterium is only destroyed so that its abundance
measured anytime, anywhere in the Universe, bounds the primordial abundance
from below. Constraints on models of post-BBN Galactic chemical evolution
follow from a comparison of the relic deuterium abundance with the
FUSE-inferred deuterium abundances in the chemically enriched, stellar
processed material of the local ISM.Comment: 8 pages, 5 figures, to appear in the Proceedings of the Future
Directions in Ultraviolet Spectroscopy Conferenc
Intergalactic Baryons in the Local Universe
Simulations predict that shocks from large-scale structure formation and
galactic winds have reduced the fraction of baryons in the warm, photoionized
phase (the Lya forest) from nearly 100% in the early universe to less than 50%
today. Some of the remaining baryons are predicted to lie in the warm-hot
ionized medium (WHIM) phase at T=10^5-10^7 K, but the quantity remains a highly
tunable parameter of the models. Modern UV spectrographs have provided
unprecedented access to both the Lya forest and potential WHIM tracers at z~0,
and several independent groups have constructed large catalogs of far-UV IGM
absorbers along ~30 AGN sight lines. There is general agreement between the
surveys that the warm, photoionized phase makes up ~30% of the baryon budget at
z~0. Another ~10% can be accounted for in collapsed structures (stars,
galaxies, etc.). However, interpretation of the ~100 high-ion (OVI, etc)
absorbers at z<0.5 is more controversial. These species are readily created in
the shocks expected to exist in the IGM, but they can also be created by
photoionization and thus not represent WHIM material. Given several pieces of
observational evidence and theoretical expectations, I argue that most of the
observed OVI absorbers represent shocked gas at T~300,000 K rather than
photoionized gas at T<30,000 K, and they are consequently valid tracers of the
WHIM phase. Under this assumption, enriched gas at T=10^5-10^6 K can account
for ~10% of the baryon budget at z<0.5, but this value may increase when bias
and incompleteness are taken into account and help close the gap on the 50% of
the baryons still "missing".Comment: Invited review to appear in "Future Directions in Ultraviolet
Spectroscopy", Oct 20-22, 2008, Annapolis, MD, M. E. Van Steenberg, ed.
(April 2009). 8 pages, five figure
The Cosmic Origins Spectrograph and the Future of Ultraviolet Astronomy
I describe the capabilities of the Cosmic Origins Spectrograph, scheduled for
May 2009 installation on the Hubble Space Telescope. With a factor-of-ten
increase in far-UV throughput for moderate resolution spectroscopy, COS will
enable a range of scientific programs that study hot stars, AGN, and gas in the
interstellar medium, intergalactic medium, and galactic halos. We also plan a
large-scale HST Spectroscopic Legacy Project for QSO absorption lines, galactic
halos, and AGN outflows. Studies of next-generation telescopes for UV/O
astronomy are now underway, including small, medium, and large missions to fill
the imminent ten-year gap between the end of Hubble and a plausible launch of
the next large mission. Selecting a strategy for achieving these goals will
involve hard choices and tradeoffs in aperture, wavelength, and capability.Comment: To appear in Future Directions in Ultraviolet Astronomy (AIP Conf
Proc
Highly Ionized Envelopes of High Velocity Clouds
We present recent results on highly ionized gas in Galactic High-Velocity
Clouds (HVCs), originally surveyed in OVI (Sembach et al. 2003). In a new
FUSE/HST survey of SiII/III/IV (Shull et al. 2009) toward 37 AGN, we detected
SiIII (lambda 1206.500 A) absorption with a sky coverage fraction 81 +/- 5% (61
HVCs along 30 of 37 high-latitude sight lines). The SiIII (lambda 1206.500 A)
line is typically 4-5 times stronger than OVI (lambda 1031.926 A). The mean HVC
column density of perhaps 10^19 cm^-2 of low-metallicity (0.1 - 0.2 Z_sun)
ionized gas in the low halo. Recent determinations of HVC distances allow us to
estimate a total reservoir of ~10^8 M_sun. Estimates of infall velocities
indicate an infall rate of around 1 M_sun yr^-1, comparable to the
replenishment rate for star formation in the disk. HVCs appear to be sheathed
by intermediate-temperature gas (10^4.0 - 10^4.5 K) detectable in SiIII and
SiIV, as well as hotter gas seen in OVI and other high ions. To prepare for HST
observations of 10 HVC-selected sight lines with the Cosmic Origins
Spectrograph (COS), we compile FUSE/STIS spectra of these ions, plus FeIII,
CIII, CIV, and SIV. Better constraints on the physical properties of HVC
envelopes and careful treatment of HVC kinematics and infall rates should come
from high-quality (S/N ~ 30-40) COS data.Comment: 3 pages, 1 figure, published in Future Directions in Ultraviolet
Spectroscopy, Proceedings of the AIP Conference held October 20-22, 2008 in
Annapolis, Marylan
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