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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 NTRS2008

[The Extrasolar Planetary Imaging Coronagraph]

The Extrasolar Planetary Imaging Coronagraph (EPIC) is a proposed NASA Exoplanet Probe mission to image and characterize extr asolar giant planets in orbits with semi-major axes between 2 and 10 AU. EPIC will provide insights into the physical nature of a variety of planets in other solar systems complimenting radial velocity (RV) and astrometric planet searches. It will detect and characterize the atmospheres of planets identified by radial velocity surveys, deter mine orbital inclinations and masses, characterize the atmospheres around A and F type stars which cannot be found with RV techniques, and observe the inner spatial structure and colors of debris disks. EPIC has a heliocentric Earth trailing drift-away orbit, with a 5 year mission lifetime (5 year goal). The robust mission design is simple and flexible ensuring mission success while minimizing cost and risk. The science payload consists of a heritage optical telescope assembly (OTA), and visible nulling coronagraph (VNC) instrument. The instrument achieves a contrast ratio of 10(exp 9) over a 4.84 arcsecond field-of-view with an unprecedented inner working angle of 0.14 arcseconds over the spectral range of 440-880 nm. The telescope is a 1.65 meter off-axis Cassegrain with an OTA wavefront error of /9, which when coupled to the VNC greatly reduces the requirements on the large scale optics, compressing them to stability requirements within the relatively compact VNC optical chain. The VNC features two integrated modular nullers, a spatial filter array (SFA) and an E2V-L3 photon counting CCD. Direct null control is accomplished from the science focal plane mitigating against complex wavefront and amplitude sensing and control strategies.

Clampin, Mark↗
NASA NTRS2008

Extrasolar Planetary Imaging Coronagraph: Visible Nulling Coronagraph Testbed Results

The Extrasolar Planetary Imaging Coronagraph (EPIC) is a proposed NASA Discovery mission to image and characterize extrasolar giant planets in orbits with semi-major axes between 2 and 10 AU. EPIC will provide insights into the physical nature of a variety of planets in other solar systems complimenting radial velocity (RV) and astrometric planet searches. It will detect and characterize the atmospheres of planets identified by radial velocity surveys, determine orbital inclinations and masses, characterize the atmospheres around A and F stars, observed the inner spatial structure and colors of inner Spitzer selected debris disks. EPIC would be launched to heliocentric Earth trailing drift-away orbit, with a 3-year mission lifetime ( 5 year goal) and will revisit planets at least three times at intervals of 9 months. The starlight suppression approach consists of a visible nulling coronagraph (VNC) that enables high order starlight suppression in broadband light. To demonstrate the VNC approach and advance it's technology readiness the NASA Goddard Space Flight Center and Lockheed-Martin have developed a laboratory VNC and have demonstrated white light nulling. We will discuss our ongoing VNC work and show the latest results from the VNC testbed,

Lyon, Richard G.↗
NASA NTRS2009

Visible Nulling Coronagraph Testbed Results

The Extrasolar Planetary Imaging Coronagraph (EPIC) is a NASA Astrophysics Strategic Mission Concept study and a proposed NASA Discovery mission to image and characterize extrasolar giant planets in orbits with semi-major axes between 2 and 10 AU. EPIC would provide insights into the physical nature of a variety of planets in other solar systems complimenting radial velocity (RV) and astrometric planet searches. It will detect and characterize the atmospheres of planets identified by radial velocity surveys, determine orbital inclinations and masses, characterize the atmospheres around A and F stars, observed the inner spatial structure and colors of inner Spitzer selected debris disks. EPIC would be launched to heliocentric Earth trailing drift-away orbit, with a 5-year mission lifetime. The starlight suppression approach consists of a visible nulling coronagraph (VNC) that enables starlight suppression in broadband light from 480-960 nm. To demonstrate the VNC approach and advance it's technology readiness we have developed a laboratory VNC and have demonstrated white light nulling. We will discuss our ongoing VNC work and show the latest results from the VNC testbed.

Lyon, Richard G.↗
NASA NTRS2018

Biosignature False Positives

In our search for life - whether within the earliest part of Earth's geologic record, on planets within our solar system such Mars, or especially for extrasolar planets - we must infer the presence of life from its impact on the local or global environment. These "biosignatures," often identified from the known influence of terrestrial organisms on the Earth's atmosphere and surface, could be misdiagnosed when we apply them to alien worlds. The so-called false positives may occur when another process or suite of processes masks or mimics a biosignature. Here, we examine several leading biosignatures, then introduce potential false positives for these signals, and finally discuss methods to discriminate between the two using current and future detection technologies. We conclude that it is the astrobiology community's responsibility to thoroughly exhaust all possibilities before we resort to "life" as an explanation.

Harman, Chester E.↗
NASA NTRS2019

Long-Duration Venus Lander Development

One of the most intriguing planets in our solar system for both solar system and extra-solar system science is Venus. Venus is the planet most similar to Earth in several key ways and many believe Venus-like planets are more common around other suns than are Earth-like planets. Therefore scientific understanding of our sister planet is a high priority. However, the hostile environmental conditions at the surface coupled with thick acid clouds and dense atmosphere have made understanding this planet very challenging. Remote sensing of surface features and near surface environments is very limited. The hostile environment has also limited the ability of landers to survive, in fact the longest living asset survived just over two hours. Even after over 50 years of attempts to explore Venus, many key measurements, especially near the surface, are still in the future. NASA has begun to undertake steps to overcome the technical challenges and is developing the capability for sustained operations and science return from this important body. For example, recent technology advances in high temperature sensors, electronics, power, and other systems have been funded and this, combined with the new capabilities to replicate Venus conditions on Earth, are changing the outlook for Venus surface exploration.

Kremic, Tibor↗
NASA NTRS2018

Solar System Expansion and Strong Equivalence Principle as Seen by the NASA MESSENGER Mission

The NASA MESSENGER mission explored the innermost planet of the solar system and obtained a rich dataset of range measurements for the determination of Mercury's ephemeris. Here we use these precise data collected over seven years to estimate parameters related to General Relativity and the evolution of the Sun. These results confirm the validity of the Strong Equivalence Principle with a significantly refined uncertainty of the Nordtvedt parameter eta=(-6.6 plus or minus 7.2)x10(exp -5) By assuming a metric theory of gravitation, we retrieved the Post-Newtonian parameter beta = 1 + (-1.6 plus or minus 1.8)x10(exp -5) and the Sun's gravitational oblateness, J(sub 2 solar)=(2.246 plus or minus 0.022)x10(exp -7). Finally, we obtain an estimate of the time variation of the Sun gravitational parameter, G (raised dot)solar mass/G solar mass =(-6.13 plus or minus 1.47)x10(exp -14), which is consistent with the expected solar mass loss due to the solar wind and interior processes. This measurement allows us to constrain |G(raised dot)|/G to be less than 4 x 10(exp -14) yr(exp -1).

Antonio Genova↗
NASA NTRS2006

Formation of the giant planets

The observed properties of giant planets, models of their evolution and observations of protoplanetary disks provide constraints on the formation of gas giant planets. The four largest planets in our Solar System contain considerable quantities of hydrogen and helium, which could not have condensed into solid planetesimals within the protoplanetary disk. All three (transiting) extrasolar giant planets with well determined masses and radii also must contain substantial amounts of these light gases. Jupiter and Saturn are mostly hydrogen and helium, but have larger abundances of heavier elements than does the Sun. Neptune and Uranus are primarily composed of heavier elements. HD 149026 b, which is slightly more massive than is Saturn, appears to have comparable quantities of light gases and heavy elements. HD 209458 b and TrES-1 are primarily hydrogen and helium, but may contain supersolar abundances of heavy elements. Spacecraft flybys and observations of satellite orbits provide estimates of the gravitational moments of the giant planets in our Solar System, which in turn provide information on the internal distribution of matter within Jupiter, Saturn, Uranus and Neptune. Atmospheric thermal structure and heat flow measurements constrain the interior temperatures of planets. Internal processes may cause giant planets to become more compositionally differentiated or alternatively more homogeneous; high-pressure laboratory .experiments provide data useful for modeling these processes. The preponderance of evidence supports the core nucleated gas accretion model. According to this model, giant planets begin their growth by the accumulation of small solid bodies, as do terrestrial planets. However, unlike terrestrial planets, the growing giant planet cores become massive enough that they are able to accumulate substantial amounts of gas before the protoplanetary disk dissipates. The primary questions regarding the core nucleated growth model is under what conditions planets with small cores/total heavy element abundances can accrete gaseous envelopes within the lifetimes of gaseous protoplanetary disks.

Lissauer, Jack J.↗
NASA NTRS2003

Factors Influencing Solar Electric Propulsion Vehicle Payload Delivery for Outer Planet Missions

Systems analyses were performed for missions utilizing solar electric propulsion systems to deliver payloads to outer-planet destinations. A range of mission and systems factors and their affect on the delivery capability of the solar electric propulsion system was examined. The effect of varying the destination, the trip time, the launch vehicle, and gravity-assist boundary conditions was investigated. In addition, the affects of selecting propulsion system and power systems characteristics (including primary array power variation, number of thrusters, thruster throttling mode, and thruster Isp) on delivered payload was examined.

Cupples, Michael↗
NASA NTRS1977

Aluminum-26 in the early solar system - Fossil or fuel

The isotopic composition of Mg was measured in different phases of a Ca-Al-rich inclusion in the Allende meteorite. Large excesses of Mg-26 of up to 10% were found. These excesses correlate strictly with the Al-27/Mg-24 ratio for four coexisting phases with distinctive chemical compositions. Models of in situ decay of Al-26 within the solar system and of mixing of interstellar dust grains containing fossil Al-26 with normal solar system material are presented. The observed correlation provides definitive evidence for the presence of Al-26 in the early solar system. This requires either injection of freshly synthesized nucleosynthetic material into the solar system immediately before condensation and planet formation, or local production within the solar system by intense activity of the early sun. Planets promptly produced from material with the inferred Al-26/Al-27 would melt within about 300,000 years.

Lee, T.↗
NASA NTRS2018

Venera-D Mission Concept to Study Atmosphere, Surface and Plasma Environment: Phase II Report of the Venera-D Joint Science Definition Team

Venus and Earth were formed approximately the same distance from the Sun, and have almost the same masses and volumes: they should be the most similar pair of planets in the Solar System. A vital, outstanding question is how and when these planets diverged in their atmospheric evolutions. Significantly, recent investigations present evidence for microbial life in Venus' cloud deck. Venus presents us with fundamental questions about the origin and evolution of planetary bodies and life in our Solar System.Venera-D (D stands for the Russian word for "long-lived:" dolgozhivushaya) is a potential mission that would combine simultaneous observations of Venus' atmosphere, plasma environment, and surface to try to answer these essential questions.

Zasova, L.↗
NASA NTRS1997

X2000 Power System Architecture

JPL is starting a new program that targets the exploration of the outer planets in our Solar System. The Advanced Deep Space System Development Program (ADSSDP) is to provdie a spacecraft system for a series of missions exploring the outer planets.

x2000↗
NASA NTRS1992

Europa: Prospects for an ocean and exobiological implications

As far as we know, Earth is the only planet in our solar system that supports life. It is natural, therefore, that our understanding of life as a planetary phenomenon is based upon Earth-like planets. There are environments in the solar system where liquid water, commonly believed to be a prerequisite for biological activity, may exist in a distinctly non-Earth-like environment. One such location is Europa, one of the Galilean satellites of Jupiter. The possibility that liquid water exists on Europa presents us with some interesting exobiological implications concerning the potential of the satellite to support life. Topics include the following: an ocean on Europa; thermal evolution of Europa; Europa's three models; exobiological implications; early conditions of Europa; low-temperature abiotic chemistry; possibility of the emergence of life on Europa; prerequisites for the habitability of Europa; energy sources for biosynthesis and metabolic activity; habitability of Europa by anaerobic life; and habitability by aerobic life.

Oro, John↗
NASA NTRS2014

Characterizing Cold Giant Planets in Reflected Light: Lessons from 50 Years of Outer Solar System Exploration and Observation

A space based coronagraph, whether as part of the WFIRST/AFTA mission or on a dedicated space telescope such as Exo-C or -S, will be able to obtain photometry and spectra of multiple gas giant planets around nearby stars, including many known from radial velocity detections. Such observations will constrain the masses, atmospheric compositions, clouds, and photochemistry of these worlds. Giant planet albedo models, such as those of Cahoy et al. (2010) and Lewis et al. (this meeting), will be crucial for mission planning and interpreting the data. However it is equally important that insights gleaned from decades of solar system imaging and spectroscopy of giant planets be leveraged to optimize both instrument design and data interpretation. To illustrate these points we will draw on examples from solar system observations, by both HST and ground based telescopes, as well as by Voyager, Galileo, and Cassini, to demonstrate the importance clouds, photochemical hazes, and various molecular absorbers play in sculpting the light scattered by solar system giant planets. We will demonstrate how measurements of the relative depths of multiple methane absorption bands of varying strengths have been key to disentangling the competing effects of gas column abundances, variations in cloud height and opacity, and scattering by high altitude photochemical hazes. We will highlight both the successes, such as the accurate remote determination of the atmospheric methane abundance of Jupiter, and a few failures from these types of observations. These lessons provide insights into technical issues facing spacecraft designers, from the selection of the most valuable camera filters to carry to the required capabilities of the flight spectrometer, as well as mission design questions such as choosing the most favorable phase angles for atmospheric characterization.

atmospheric methane abundance↗
NASA NTRS1985

What color is the solar system?

Estimates are made of the true visual colors of various planets and moons in the solar system. Account is taken of the components of perceived color, i.e., hue, saturation and lightness. Earth is a blue planet while most of the others, including Mars, are yellow and differ only in their lightness. Widely disseminated Voyager images of Jupiter have been computer-enhanced to highlight details. A reflectance spectrum established by the International Commission on Illumination provides reference lines which are measured and compared with reference colors which would be seen on earth in normal daylight. Uranus is actually a light aqua color due to its absorption of 6190 A light and reflectance of 5000 A blue green light.

Young, A. T.↗
NASA NTRS2002

The Discovery of Extrasolar Planets by Backyard Astronomers

The discovery since 1995 of more than 80 planets around nearby solar-like stars and the photometric measurement of a transit of the jovian mass planet orbiting the solar-like star HD 209458 (producing a more than 1% drop in brightness that lasts 3 hours) has heralded a new era in astronomy. It has now been demonstrated that small telescopes equipped with sensitive and stable electronic detectors can produce fundamental scientific discoveries regarding the frequency and nature of planets outside the solar system. The modest equipment requirements for the discovery of extrasolar planetary transits of jovian mass planets in short period orbits around solar-like stars are fulfilled by commercial small aperture telescopes and CCD (charge coupled device) imagers common among amateur astronomers. With equipment already in hand and armed with target lists, observing techniques and software procedures developed by scientists at NASA's Ames Research Center and the University of California at Santa Cruz, non-professional astronomers can contribute significantly to the discovery and study of planets around others stars. In this way, we may resume (after a two century interruption!) the tradition of planet discoveries by amateur astronomers begun with William Herschel's 1787 discovery of the 'solar' planet Uranus.

Castellano, Tim↗
NASA NTRS2005

Accuracy and stability of fringe measurements in SIM

In order to identify habitable planets beyond our solar system it is necessary to determine their masses. SIM PlanetQuest is the only space mission which can discover and measure planets as small and cool as those in our solar system. This mission, however, requires unprecedented accuracy of angular rneasurements to the level of a microarcsecond, which are three orders of magnitude better than accuracy of the recent space astrometric missions. For microarcsecond accuracy of astrometric measurements the corresponding fringe delay must be determined to the accuracy of picometers, and it is a challenging task to measure fringe delays to this level of precision.

interferometer↗
NASA NTRS1982

A search for fragmentation debris near Ursa Major Stream stars

Accretion models of planet formation and the early cratering history of the solar system suggest that planet formation is accompanied by a cloud of debris resulting from accumulation and fragmentation. A rough estimate of the infrared luminosities of debris clouds is presented for comparison with measured 10-micron luminosities of young stars. New measurements of 13 F, G, and K main-sequence stars of the Ursa Major Stream, which is thought to be about 270-million years old, place constraints on the amount of debris which could be present near these stars.

Witteborn, F. C.↗