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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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NASA NTRS2017

The Saturn System Through the Eyes of Cassini

More than 400 years ago, Galileo Galilei trained his homemade telescope on the night sky and observed that Saturn had two objects closely related to the planet extending on either side. At the time, in 1610, Galileo declared them to be moons. A few decades later, Saturn moon science accelerated at a dizzying pace. Christiaan Huygens first observed Saturn's largest moon Titan in 1655 and was the first to describe the extended moon-like features at Saturn as a disk of material sounding the planet. From 1671 to 1674, Giovanni Cassini discovered the moons lapetus, Rhea, Dione and Tethys. In 1675, Cassini discovered the gap in Saturn's rings that we now know as the Cassini Division. In the space age, before the Cassini-Huygens mission, we had only hints of the discoveries awaiting us at Saturn. Pioneer 11 and Voyagers 1 and 2 conducted flybys decades ago. But these quick encounters didn't allow time for more extensive research. NASA and the European Space Agency created a partnership to orbit a Saturn orbiter (Cassini) and a lander (Huygens) on Titan. Like its namesakes, the Cassini-Huygens mission not only discovered previously unknown moons, but it also helped us understand the science behind their formation, their interactions with the rings, and how truly diverse they are. The Cassini-Huygens mission revolutionized what we know about the Saturn system. The rings of Saturn, the moons, and the planet itself offer irresistible and inexhaustible subjects for intense study, and Cassini-Huygens did not disappoint. The Saturnian system proved to be a rich ground for science exploration and discoveries, and Cassini has been nothing short of a discovery machine. At the time Cassini plunged into Saturn at the end of its mission, it had observed the planet for a little less than half of a Saturn year. But it also orbited the gas giant 293 times, forever changing our understanding of the Saturn system and yielding tremendous insight for understanding the entire Solar System.

Green, James↗
NASA NTRS2021

Starshade Rendezvous: Exoplanet Sensitivity and Observing Strategy

Launching a starshade to rendezvous with the Nancy Grace Roman Space Telescope (Roman) would provide the first opportunity to directly image the habitable zones (HZs) of nearby sunlike stars in the coming decade. A report on the science and feasibility of such a mission was recently submitted to NASA as a probe study concept. The driving objective of the concept is to determine whether Earth-like exoplanets exist in the HZs of the nearest sunlike stars and have biosignature gases in their atmospheres. With the sensitivity provided by this telescope, it is possible to measure the brightness of zodiacal dust disks around the nearest sunlike stars and establish how their population compares with our own. In addition, known gas-giant exoplanets can be targeted to measure their atmospheric metallicity and thereby determine if the correlation with planet mass follows the trend observed in the Solar System and hinted at by exoplanet transit spectroscopy data. We provide the details of the calculations used to estimate the sensitivity of Roman with a starshade and describe the publicly available Python-based source code used to make these calculations. Given the fixed capability of Roman and the constrained observing windows inherent for the starshade, we calculate the sensitivity of the combined observatory to detect these three types of targets, and we present an overall observing strategy that enables us to achieve these objectives.

Andrew Frederic Romero-wolf↗
NASA NTRS1992

International Ultraviolet Explorer (IUE) ultraviolet spectral atlas of selected astronomical objects

The IUE Ultraviolet Spectral Atlas of Selected Astronomical Objects (or 'the Atlas'), is based on the data that were available in the IUE archive in 1986, and is intended to be a quick reference for the ultraviolet spectra of many categories of astronomical objects. It shows reflected sunlight from the Moon, planets, and asteroids, and also shows emission from comets. Comprehensive compilations of UV spectra for main sequence, subgiant, giant, bright giant, and supergiant stars are published elsewhere. This Atlas contains the spectra for objects occupying other areas of the Hertzsprung-Russell diagram: pre-main sequence stars, chemically peculiar stars, pulsating variables, subluminous stars, and Wolf-Rayet stars. This Atlas also presents phenomena such as the chromospheric and transition region emissions from late-type stars; composite spectra of stars, gas streams, accretion disks and gas envelopes of binary systems; the behavior of gas ejecta shortly after the outburst of novac and supernovac; and the H II regions, planetary nebulae, and supernova remnants. Population 2 stars, globular clusters, and luminous stars in the Magellanic Clouds, M31, and M33, are also included in this publication. Finally, the Atlas gives the ultraviolet spectra of galaxies of different Hubble types and of active galaxies.

Wu, Chi-Chao↗
NASA NTRS1993

The atmospheres of Uranus and Neptune

The atmospheres of Uranus and Neptune are discussed in the light of the Voyager 2 flybys of these planets. A basic overview of their atmospheres is presented, with emphasis on thermal structure, composition, energy and opacity sources, cloud structure, and the horizontal structure of the atmospheres. The nature and implications of the different internal heat flows on the two planets, and the implications of the deuterium and helium abundances for the origin and evolution of these ice giants, as distinct from Jupiter and Saturn, are discussed. Selected chemical and physical processes in the atmospheres of Uranus and Neptune are illustrated.

Lunine, Jonathan I.↗
NASA NTRS2019

Measuring the D/H Ratios of Exoplanets and Brown Dwarfs

The relative abundance of deuterium and hydrogen is a potent tracer of planet formation and evolution. Jupiter and Saturn have protosolar atmospheric D/H ratios, a relic of substantial gas accretion from the nebula, while the atmospheres of Neptune and Uranus are enhanced in D by accretion of ices into their envelopes. For terrestrial planets, D/H ratios are used to determine the mechanisms of volatile delivery and subsequent atmosphere loss over the lifetime of the planet. Planets and brown dwarfs more massive than ~13 M(J) quickly fuse their initial D reservoir. Here, we simulate spectra for giant exoplanets and brown dwarfs (2 M(Neptune) to ~10 M(Jupiter)) from T(eff) = 200–1800 K including both CH3D and HDO to determine the observability of these dominant deuterium isotopologues in mid-infrared thermal emission spectra. Colder objects have stronger molecular features in their spectra, due to the temperature dependence of molecular cross sections. CH3D is easier to observe than HDO at all temperatures considered, due to the strength of its absorption bands and locations of features at wavelengths with few other strong absorption features. We predict that for nearby cool brown dwarfs, the CH3D abundance can be measured at high signal to noise with the James Webb Space Telescope (JWST); for objects from 200 to 800 K closer than 10 pc, a protosolar D/H ratio would be readily observable in 2.5 hr. Moderately young Jupiter-mass planets (100–300 Myr) and young Neptunes (10 Myr) may be discovered with JWST and provide the best targets for detecting deuterium on an exoplanet in the coming decade. Future telescope designs should consider the importance of isotopes for understanding the formation and evolution of planetary atmospheres.

Caroline V. Morley↗
NASA NTRS1993

Giant impact-induced atmospheric blow-off

The relationship between the present atmospheres of the Earth, Venus, and Mars and the earliest (primordial) atmospheres which surrounded these planets is discussed. The termination of the co-accretion of an atmosphere results from at least three different mechanisms, and these mechanisms are presented. To calculate the energy, and hence, approximate planetesimal size, such that upon impact the entire planetary atmosphere is blown off, a different approach than previous efforts is employed, and a shock wave that is entirely propagated within a terrestrial planet is considered.

Ahrens, Thomas J.↗
NASA NTRS1996

Ways that our Solar System helps us understand the formation of other planetary systems and ways that it doesn't

Models of planetary formation can be tested by comparison of their ability to predict features of our Solar System in a consistent way, and then extrapolated to other hypothetical planetary systems by different choice of parameters. When this is done, it is found that the resulting systems are insensitive to direct effects of the mass of the star, but do strongly depend on the properties of the disk, principally its surface density. Major uncertainty results from lack of an adequate theoretical model that predicts the existence, size, and distribution of analogs of our Solar System, particularly the gas giants Jupiter and Saturn. Nevertheless, reasons can be found for expecting that planetary systems, including those containing biologically habitable planets similar to Earth, may be abundant in the Galaxy and Universe.

NASA Discipline Exobiology↗
NASA NTRS2005

The Core of the Moon - Molten or Solid?

While several studies beginning in the Apollo era and continuing up to the present have tried to detect the lunar core, either geochemically, geophysically or geologically [e.g. 1, 2, 3, 4], it has so far proven somewhat elusive. The unambiguous detection of the lunar core is of prime importance as it holds the potential of distinguishing between the various theories for the formation of the Moon. The theory which currently enjoys the greatest success is the giant impact model, which has the Moon forming about 4.5 Gyr ago from the debris produced when a Mars sized proto planet collided with the proto Earth [e.g. 5, 6]. Simulations reveal that the material from which the Moon is made up contains very little iron and consequently a lunar core, if it exists, should be small.

Khan, A.↗
NASA NTRS2009

Antennas Lower Cost of Satellite Access

Whether for scientific inquiry, weather forecasting, or public safety, the world relies upon the data gathered by satellite remote sensing. Some of NASA s most valuable work is in its remote sensing capabilities - the ability to retrieve data acquired at great distances - affording a height and scope not available from the ground. NASA satellites in low Earth orbit (LEO) monitor ocean health by taking large-scale pictures of phytoplankton blooms and measuring surface temperatures; snap photographs of full hurricanes from above, teaching researchers about how these giant storms form; and capture images of cloud formation and air pollution, all allowing researchers to further develop understanding of the planet s health. NASA remote sensing satellites also monitor shifts in the Earth s crust, analyze wind patterns around the world to develop efficient wind energy, help people around the world recover from natural disasters, and monitor diminishing sea ice levels. Just as researchers are more heavily relying on this data from space to conduct their work, the instruments carried on satellites are getting more sophisticated and capable of capturing increasingly complex and accurate measurements. The satellites are covering larger areas, from farther away, and generating more and more valuable data. The ground-based receivers for this wealth of satellite data have grown increasingly capable of handling greater bandwidth and higher power levels. They have also become less expensive, through a NASA research partnership, with the creation of a high-rate X-band data receiver system that is now in widespread use around the globe.

Source record↗
NASA NTRS2010

Extrasolar Planets Observed with JWST and the ELTs

The advent of cryogenic space-borne infrared observatories such as the Spitzer Space Telescope has lead to a revolution in the study of planets and planetary systems orbiting sun-like stars. Already Spitzer has characterized the emergent infrared spectra of close-in giant exoplanets using transit and eclipse techniques. The James Webb Space Telescope (JWST) will be able to extend these studies to superEarth exoplanets orbiting in the habitable zones of M-dwarf stars in the near solar neighborhood. The forthcoming ground-based Extremely Large Telescopes (ELTs) will playa key role in these studies, being especially valuable for spectroscopy at higher spectral resolving powers where large photon fluxes are needed. The culmination of this work within the next two decades will be the detection and spectral characterization of the major molecular constituents in the atmosphere of a habitable superEarth orbiting a nearby lower main sequence star.

Deming, L. Drake↗
NASA NTRS2021

TOI-2109: An Ultrahot Gas Giant on a 16 hr Orbit

We report the discovery of an ultrahot Jupiter with an extremely short orbital period of 0.67247414 ± 0.00000028 days (∼16 hr). The 1.347 ± 0.047 RJup planet, initially identified by the Transiting Exoplanet Survey Satellite (TESS) mission, orbits TOI-2109 (TIC 392476080)—a T(eff) ∼ 6500 K F-type star with a mass of 1.447 ± 0.077 Mꙩ, a radius of 1.698 ± 0.060 Rꙩ, and a rotational velocity of v sin i =81.9 ± 1.7 km/s. The planetary nature of TOI-2109b was confirmed through radial-velocity measurements, which yielded a planet mass of 5.02 ± 0.75 M(Jup). Analysis of the Doppler shadow in spectroscopic transit observations indicates a well-aligned system, with a sky-projected obliquity of λ = 1.°7± 1.°7. From the TESS full-orbit light curve, we measured a secondary eclipse depth of 731 ± 46 ppm, as well as phase-curve variations from the planet's longitudinal brightness modulation and ellipsoidal distortion of the host star. Combining the TESS-band occultation measurement with a K(s)-band secondary eclipse depth (2012 ± 80 ppm) derived from ground-based observations, we find that the dayside emission of TOI-2109b is consistent with a brightness temperature of 3631 ± 69 K, making it the second hottest exoplanet hitherto discovered. By virtue of its extreme irradiation and strong planet–star gravitational interaction, TOI-2109b is an exceptionally promising target for intensive follow-up studies using current and near-future telescope facilities to probe for orbital decay, detect tidally driven atmospheric escape, and assess the impacts of H2 dissociation and recombination on the global heat transport.

Ian Wong↗
NASA NTRS1985

The impact ejection of living organisms into space

The possibility of natural processes to blast living organisms into space was examined. It is suggested that rocks ejected from the Earth by a giant meteorite or comet impact can carry microorganisms into space. Such microscopic Earth life would have an opportunity to colonize the other planets if it can survive the rigors of space until it falls into the atmosphere of a hospitable planet.

Melosh, H. J.↗
NASA NTRS2008

High-Resolution N-Band Observations of the Nova Rs Ophiuchi: First Science with the Keck Interferometer Nuller

We report new observations of the nova RS Ophiuchi using the Keck Interferometer Nulling Instrument (KIN), approximately 3.8 days following the most recent outburst that occurred on 2006 February 12. These observations represent the first scientific results from the KIN, which operates in N-band from 8 to 12.5 microns. The nulling technique is the sparse aperture equivalent of the conventional coronagraphic technique used in filled aperture telescopes. By fitting the unique KIN inner and outer spatial regime data, we have obtained an angular size of the mid-infrared continuum of 6.2,4.0, or 5.4 mas for a disk profile, Gaussian profile, and shell profile respectively. The data show evidence of enhanced neutral atomic hydrogen emission and atomic metals including silicon located in the inner spatial regime near the white dwarf relative to the outer regime. There are also nebular emission lines and evidence of hot silicate dust in the outer spatial region, centered at approximately 2.5E14 cm from the WD, that are not found in the inner regime. The nova flash in the outer spatial regime evidently excited these features before the blast wave reached these regions. These identifications support the following interpretation. The dust appears to be present between outbursts and was not created during the outburst event. We further discuss the present results in terms of a unifying model of the system that includes an increase in density in the plane of the orbit of the two stars created by a spiral shock wave caused by the motion of the stars through the cool wind of the red giant star. These data show the power and potential of the nulling technique which has been developed for the detection of Earthlike planets around nearby stars for the Terrestrial Planet Finder Mission and Darwin missions.

Danchi, William↗
NASA NTRS2003

The Kepler Mission: A Search for Terrestrial Planets - Development Status

We have embarked on a mission to detect terrestrial planets. The space mission has been optimized to search for earth-size planets (0.5 to 10 earth masses) in the habitable zone (HZ) of solar-like stars. Given this design, the mission will necessarily be capable of not only detecting Earth analogs, but a wide range of planetary types and characteristics ranging from Mercury-size objects with orbital periods of days to gas-giants in decade long orbits that have undeniable signatures even with only one transit detected. The mission is designed to survey the full range of spectral-type dwarf stars. The approach is to detect the periodic signal of transiting planets. Three or more transits of a star exceeding a combined threshold of eight sigma with a statistically consistent period, brightness change and duration provide a rigorous method of detection. From the relative brightness change the planet size can be calculated. From the period the orbital size can be calculated and its location relative to the HZ determined. Presented here are: the mission goals, the top level system design requirements derived from these goals that drive the flight system design, a number of the trades that have lead to the mission concept, expected photometric performance dependence on stellar brightness and spectral type based on the system 'noise tree' analysis. Updated estimates are presented of the numbers of detectable planets versus size, orbit, stellar spectral type and distances based on a planet frequency hypothesis. The current project schedule and organization are given.

Koch, David↗
NASA NTRS2017

Characterizing K2 Candidate Planetary Systems Orbiting Low-Mass Stars. I. Classifying Low-Mass Host Stars Observed During Campaigns 1-7

We present near-infrared spectra for 144 candidate planetary systems identified during Campaigns 1-7 of the NASA K2 Mission. The goal of the survey was to characterize planets orbiting low-mass stars, but our Infrared Telescope Facility/SpeX and Palomar/TripleSpec spectroscopic observations revealed that 49% of our targets were actually giant stars or hotter dwarfs reddened by interstellar extinction. For the 72 stars with spectra consistent with classification as cool dwarfs (spectral types K3-M4), we refined their stellar properties by applying empirical relations based on stars with interferometric radius measurements. Although our revised temperatures are generally consistent with those reported in the Ecliptic Plane Input Catalog (EPIC), our revised stellar radii are typically 0.13 solar radius (39%) larger than the EPIC values, which were based on model isochrones that have been shown to underestimate the radii of cool dwarfs. Our improved stellar characterizations will enable more efficient prioritization of K2 targets for follow-up studies.

Campaigns17 of the NASA K2 Mission↗
NASA NTRS2008

First Science with the Keck Interferometer Nuller High Spatial Resolution N-Band Observations of the Recurrent Nova RS Ophiuchi

We report observations of the nova RS 0phiuchi using the Keck Interferometer Nuller (KIN) taken approximately 3.8 days following the most recent outburst that occurred on 2006 February 12. The KIN operates in N-band from approx. 8 to 12.5 microns in a nulling mode - the sparse aperture equivalent of the conventional coronagraphic technique used in filled aperture te1escopes. In this mode the stellar light is suppressed by a destructive fringe, effectively enhancing the contrast of the circumstellar material located near the star. In a second, constructive-fringe mode, the instrument detects primarily the light from the central, bright source. These are the outer and inner spatial regimes, resprectively. We will describe the capabilities of the KIN, including these unique modes, and outline how they were key in our discovery that dust does not appear to be created in the outburst as in previous models, but instead was created between nova events. We also show how these first results from the KIN are consistent with Spitzer data. The KIN data show evidence of enhanced neutral atomic hydrogen emission and atomic metals including silicon located in the inner spatial regime near the white dwarf (WD) relative to the outer regime. There are also nebular emission lines and evidence of hot silicate dust in the outer spatial region, centered at approximately 17 AU from the WD, that are not found in the inner regime. The KIN and Spitzer data suggest that these emissions were excited by the nova flash in the outer spatial regime before the blast wave reached these regions. We describe the present results in terms of a new model for dust creation in recurrent novae that includes an increase in density in the plane of the orbit of the two stars created by a spiral shock wave caused by the motion of the stars through the cool wind of the red giant star. These data show the power and potential of the nulling technique which has been developed for the detection of Earth-like planets around nearby stars for the Terrestrial Planet Finder and Darwin missions.

Barry, Richard K.↗
NASA NTRS2007

High-Resolution N-Band Observations of the Nova RS Ophiuchi with the Keck Interferometer Nuller

We report new observations of the nova RS Ophiuchi (RS Oph) using the Keck Interferometer Nulling Instrument, approximately 3.8 days following the most recent outburst that occurred on 2006 February 12. The Keck Interferometer Nuller (KIN) operates in K-band from 8 to 12.5 pm in a nulling mode, which means that the central broad-band interference fringe is a dark fringe - with an angular width of 25 mas at mid band - rather than the bright fringe used ill a conventional optical interferometer. In this mode the stellar light itself is suppressed by the destructive fringe, effectively enhancing the contrast of the circumstellar material located near the star. By subsequently shifting the neighboring bright fringe onto the center of the source brightness distribution and integrating, a second spatial regime dominated by light from the central portion of the source is almost simultaneously sampled. The nulling technique is the sparse aperture equivalent of the conventional corongraphic technique used in filled aperture telescopes. By fitting the unique KIK inner and outer spatial regime data, we have obtained an angular size of the mid-infrared continuum of 6.2, 4.0. or 5.4 mas for a disk profile, gaussian profile (fwhm), and shell profile respectively. The data show evidence of enhanced neutral atomic hydrogen emission located in the inner spatial regime relative to the outer regime. There is also evidence of a 9.7 micron silicate feature seen outside of this region. Importantly, we see spectral lines excited by the nova flash in the outer region before the blast wave reaches these regions. These lines are from neutral, weakly excited atoms which support the following interpretation. We discuss the present results in terms of a unifying model of the system that includes an increase in density in the plane of the orbit of the two stars created by a spiral shock wave caused by the motion of the stars through the cool wind of the red giant star. These data show the power and potential of the nulling technique which has been developed for the detection of Earth-like planets around nearby stars for the Terrestrial Planet Finder Mission and Darwin missions.

Barry, R. K.↗
NASA NTRS2012

WISE Detections of Dust in the Habitable Zones of Planet-Bearing Stars

We use data from the Wide-field Infrared Survey Explorer (WISE) all-sky release to explore the incidence of warm dust in the habitable zones around exoplanet-host stars. Dust emission at 12 and/or 22 microns (T(sub dust) approx.300 and/or approx.150 K) traces events in the terrestrial planet zones; its existence implies replenishment by evaporation of comets or collisions of asteroids, possibly stirred by larger planets. Of the 591 planetary systems (728 extrasolar planets) in the Exoplanet Encyclopedia as of 2012 January 31, 350 are robustly detected by WISE at > or = 5(sigma) level. We perform detailed photosphere subtraction using tools developed for Spitzer data and visually inspect all the WISE images to confirm bona fide point sources. We find nine planet-bearing stars show dust excess emission at 12 and/or 22 microns at > or = 3(sigma) level around young, main-sequence, or evolved giant stars. Overall, our results yield an excess incidence of approx.2.6% for stars of all evolutionary stages, but approx.1% for planetary debris disks around main-sequence stars. Besides recovering previously known warm systems, we identify one new excess candidate around the young star UScoCTIO 108.

Morales, Farisa Y.↗