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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Deep space network - systems design, communications engineering developments and research, and tracking stations engineering and operations
Deep Space Network /DSN/ for two way communications with unmanned spacecraft travelling to inteplanetary distances
Tracking and navigation, communications R&D, ground support equipment, and computer programming for deep space network
Tracking and navigation analysis, communications development, and facility engineering and operations for deep space network
As astronauts venture farther from Earth, and for longer periods, food will become increasingly critical. Crop production can supplement a packaged diet to provide additional nutrients and variety for astronauts. Testing with the Veggie chamber on the International Space Station is allowing us to understand the impacts of gravity and spaceflight on crop growth and nutritional content, and the importance of plants to astronauts living and working away from our blue home planet.
As astronauts venture farther from Earth, and for longer periods, food will become increasingly critical. Crop production can supplement a packaged diet to provide additional nutrients and variety for astronauts. Testing with the Veggie chamber on the International Space Station is allowing us to understand the impacts of gravity and spaceflight on crop growth and nutritional content, and the importance of plants to astronauts living and working away from our blue home planet.
As astronauts venture farther from Earth, and for longer periods, food will become increasingly critical. Crop production can supplement a packaged diet to provide additional nutrients and dietary variety for astronauts. Several unique challenges exist for growth of plants in microgravity and on other planetary surfaces. Testing with the Veggie chamber on the International Space Station is allowing us to understand the impacts of gravity and spaceflight on crop growth and nutritional content, and the importance of plants to astronauts living and working away from our blue home planet.
As astronauts venture farther from Earth, and for longer periods, food will become increasingly critical. Crop production can supplement a packaged diet to provide additional nutrients and dietary variety for astronauts. Several unique challenges exist for growth of plants in microgravity and on other planetary surfaces. Testing with the Veggie chamber on the International Space Station is allowing us to understand the impacts of gravity and spaceflight on crop growth and nutritional content, and the importance of plants to astronauts living and working away from our blue home planet.
As astronauts venture farther from Earth, and for longer periods, food will become increasingly critical. Crop production can supplement a packaged diet to provide additional nutrients and dietary variety for astronauts. Several unique challenges exist for growth of plants in microgravity and on other planetary surfaces. Testing with the Veggie chamber on the International Space Station is allowing us to understand the impacts of gravity and spaceflight on crop growth and nutritional content, and the importance of plants to astronauts living and working away from our blue home planet
Fresh, nutritious, palatable produce for crew consumption on long-duration spaceflight missions may provide health-promoting, bioavailable nutrients and enhance the dietary experience. VEG-04A and VEG-04B explored growing leafy greens on the International Space Station using the Veggie Vegetable Production System. Two flight tests with ground controls were conducted in 2019 growing mizuna mustard, where Veggie chambers were set to different red-to-blue-to-green light formulations. Light quality affects plant growth, nutrition, microbiology, and organoleptic characteristics on Earth, and we examined how these vary in microgravity and under different harvest scenarios. Astronauts harvested and weighed mizuna and completed organoleptic evaluations. Flight samples were returned to Earth for nutritional quality and microbial food safety analyses. Yield and chemistry differed between ground and flight samples and light treatments, and bacterial and fungal counts were lower in ground than in flight samples. This research helps increase our understanding of the requirements for growing high-quality crops in spaceflight.
We performed self-consistent modelling of nonlinear electrotransport and electromechanical response of thin films of mixed ionic-electronic conductors (MIEC) allowing for steric effects of mobile charged defects (ions, protons, or vacancies), electron degeneration, and Vegard stresses. We establish correlations between the features of the nonlinear space-charge dynamics, current-voltage, and bending-voltage curves for different types of the film electrodes. A pronounced ferroelectric-like hysteresis of the bending-voltage loops and current maxima on the double hysteresis current-voltage loops appear for the electron-transport electrodes. The double hysteresis loop with pronounced humps indicates a memristor-type resistive switching. The switching occurs due to the strong nonlinear coupling between the electronic and ionic subsystems. A sharp meta-stable maximum of the electron density appears near one open electrode and moves to another one during the periodic change of applied voltage. Our results can explain the nonlinear nature and correlation of electrical and mechanical memory effects in thin MIEC films. The analytical expression proving that the electrically induced bending of MIEC films can be detected by interferometric methods is derived.
Despite its importance, state-of-the-art algorithms for performing complete active space self-consistent field (CASSCF) computations have lagged far behind those for single reference methods. We develop an algorithm for the CASSCF orbital optimization that uses sparsity in the atomic orbital (AO) basis set to increase the applicability of CASSCF. Our implementation of this algorithm uses graphical processing units (GPUs) and has allowed us to perform CASSCF computations on molecular systems containing more than one thousand atoms. Additionally, we have implemented analytic gradients of the CASSCF energy; the gradients also benefit from GPU acceleration as well as sparsity in the AO basis.
We present the first absolute proper motion measurement of Leo I, based on two epochs of Hubble Space Telescope ACS/WFC images separated by {approx}5 years in time. The average shift of Leo I stars with respect to {approx}100 background galaxies implies a proper motion of ({mu}{sub W}, {mu}{sub N}) = (0.1140 {+-} 0.0295, -0.1256 {+-} 0.0293) mas yr{sup -1}. The implied Galactocentric velocity vector, corrected for the reflex motion of the Sun, has radial and tangential components V{sub rad} = 167.9 {+-} 2.8 km s{sup -1} and V{sub tan} = 101.0 {+-} 34.4 km s{sup -1}, respectively. We study the detailed orbital history of Leo I by solving its equations of motion backward in time for a range of plausible mass models for the Milky Way (MW) and its surrounding galaxies. Leo I entered the MW virial radius 2.33 {+-} 0.21 Gyr ago, most likely on its first infall. It had a pericentric approach 1.05 {+-} 0.09 Gyr ago at a Galactocentric distance of 91 {+-} 36 kpc. We associate these timescales with characteristic timescales in Leo I's star formation history, which shows an enhanced star formation activity {approx}2 Gyr ago and quenching {approx}1 Gyr ago. There is no indication from our calculations that other galaxies have significantly influenced Leo I's orbit, although there is a small probability that it may have interacted with either Ursa Minor or Leo II within the last {approx}1 Gyr. For most plausible MW masses, the observed velocity implies that Leo I is bound to the MW. However, it may not be appropriate to include it in models of the MW satellite population that assume dynamical equilibrium, given its recent infall. Solution of the complete (non-radial) timing equations for the Leo I orbit implies an MW mass M{sub MW,vir} = 3.15{sub -1.36}{sup +1.58} x 10{sup 12} M{sub Sun }, with the large uncertainty dominated by cosmic scatter. In a companion paper, we compare the new observations to the properties of Leo I subhalo analogs extracted from cosmological simulations.
We describe the first results from a six-month long reverberation-mapping experiment in the ultraviolet based on 171 observations of the Seyfert 1 galaxy NGC 5548 with the Cosmic Origins Spectrograph on the Hubble Space Telescope. Significant correlated variability is found in the continuum and broad emission lines, with amplitudes ranging from ∼30% to a factor of two in the emission lines and a factor of three in the continuum. The variations of all the strong emission lines lag behind those of the continuum, with He ii λ1640 lagging behind the continuum by ∼2.5 days and Lyα λ1215, C iv λ1550, and Si iv λ1400 lagging by ∼5–6 days. The relationship between the continuum and emission lines is complex. In particular, during the second half of the campaign, all emission-line lags increased by a factor of 1.3–2 and differences appear in the detailed structure of the continuum and emission-line light curves. Velocity-resolved cross-correlation analysis shows coherent structure in lag versus line of sight velocity for the emission lines; the high-velocity wings of C iv respond to continuum variations more rapidly than the line core, probably indicating higher velocity broad-line region clouds at smaller distances from the central engine. The velocity-dependent response of Lyα, however, is more complex and will require further analysis.
We investigate the potential for the LISA space-based interferometer to detect the stochastic gravitational wave background produced from different mechanisms during inflation. Focusing on well-motivated scenarios, we study the resulting contributions from particle production during inflation, inflationary spectator fields with varying speed of sound, effective field theories of inflation with specific patterns of symmetry breaking and models leading to the formation of primordial black holes. The projected sensitivities of LISA are used in a model-independent way for various detector designs and configurations. We demonstrate that LISA is able to probe these well-motivated inflationary scenarios beyond the irreducible vacuum tensor modes expected from any inflationary background.
We make use of the Hubble Space Telescope proper-motion catalogs derived by Bellini et al. to produce the first radial velocity dispersion profiles σ(R) for blue straggler stars (BSSs) in Galactic globular clusters (GCs), as well as the first dynamical estimates for the average mass of the entire BSS population. We show that BSSs typically have lower velocity dispersions than stars with mass equal to the main-sequence turnoff mass, as one would expect for a more massive population of stars. Since GCs are expected to experience some degree of energy equipartition, we use the relation σ∝M{sup −η}, where η is related to the degree of energy equipartition, along with our velocity dispersion profiles to estimate BSS masses. We estimate η as a function of cluster relaxation from recent Monte Carlo cluster simulations by Bianchini et al. and then derive an average mass ratio M{sub BSS}/M{sub MSTO}=1.50±0.14 and an average mass M{sub BSS}=1.22±0.12 M {sub ⊙} from 598 BSSs across 19 GCs. The final error bars include any systematic errors that are random between different clusters, but not any potential biases inherent to our methodology. Our results are in good agreement with the average mass of M{sub BSS}=1.22±0.06 M {sub ⊙} for the 35 BSSs in Galactic GCs in the literature with properties that have allowed individual mass determination.
We observed the nearby millisecond pulsar J2124–3358 with the Hubble Space Telescope in broad far-UV (FUV) and optical filters. The pulsar is detected in both bands with fluxes F(1250–2000 Å) = (2.5 ± 0.3) × 10{sup −16} erg s{sup −1} cm{sup −2} and F(3800–6000 Å) = (6.4 ± 0.4) × 10{sup −17} erg s{sup −1} cm{sup −2}, which corresponds to luminosities of ≈5.8 × 10{sup 27} and 1.4 × 10{sup 27} erg s{sup −1}, for d = 410 pc and E(B − V) = 0.03. The optical-FUV spectrum can be described by a power-law model, f{sub ν}∝ν{sup α}, with slope α = 0.18–0.48 for a conservative range of color excess, E(B − V) = 0.01–0.08. Since a spectral flux rising with frequency is unusual for pulsar magnetospheric emission in this frequency range, it is possible that the spectrum is predominantly magnetospheric (power law with α < 0) in the optical, while it is dominated by thermal emission from the neutron star surface in the FUV. For a neutron star radius of 12 km, the surface temperature would be between 0.5 × 10{sup 5} and 2.1 × 10{sup 5} K for α ranging from −1 to 0, E(B − V) = 0.01–0.08, and d = 340–500 pc. In addition to the pulsar, the FUV images reveal extended emission that is spatially coincident with the known Hα bow shock, making PSR J2124–3358 the second pulsar (after PSR J0437−4715) with a bow shock detected in the FUV.
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