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At least 631 records · Page 35
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Physics of planetary atmospheres and ionospheres

The traditional atmospheric regions, the distinction between homosphere and heterosphere, and changing atmospheric composition are discussed. The validity of the barometric law based on a Maxwell-Boltzmann distribution, for the major part of a planetary atmosphere and its breakdown in the exosphere due to escape of atmospheric particles is considered. The formation and maintenance of photochemical and diffusion-controlled ionospheric layers are treated. Their applicability to planetary ionospheres is dealt with. The spatial extent of magnetic and nonmagnetic planet ionospheres is investigated. Thermal and nonthermal processes responsible for the mass loss of planetary atmospheres are surveyed.

Bauer, S. J.↗
NASA NTRS1984

The unique planetary nebula NGC 2818

The planetary nebula NGC 2818, or PK 261 + 8 deg 1, is of special interest due to its apparent association with a Population I open cluster (of the same designation). The results of new observations of the nebula are presented, including interference-filter imagery, photoelectric photometry, and ground-based and IUE spectroscopy. Analysis of its composition based on new IUE and ground-based spectroscopy and model calculations of the very similar planetary nebula NGC 2440 suggests that NGC 2818 is a prototype of the He-rich and N-rich Type I group. Compared to the composition of H II regions in the solar neighborhood, He is 60 percent overabundant, C is 0.3 dex lower, N is 1.0 dex higher, and O, Ne, Si, Cl, and Ar are essentially at comparable values. Analysis of kinematical and morphological data suggests that the nebula is probably associated with the star cluster (revised distance = 3.5 kpc). If so, then it is of exceptional size (radius approximately 1.1 pc), mass (greater than or equal to 0.6 solar mass), expansion velocity (52 + or - 3 km/s), and age (possibly as old as 22,000 yr). Some implications of the results regarding the masses of planetary-nebula progenitors, the nucleosynthesis processes in stars of intermediate mass, and the formation of planetary nebulae are also discussed.

Dufour, R. J.↗
NASA NTRS2013

Highly Sensitive Tunable Diode Laser Spectrometers for In Situ Planetary Exploration

This paper describes highly sensitive tunable diode laser spectrometers suitable for in situ planetary exploration. The technology developed at JPL is based on wavelength modulated cavity enhanced absorption spectroscopy. It is capable of sensitively detecting chemical signatures of life through the abundance of biogenic molecules and their isotopic composition, and chemicals such as water necessary for habitats of life. The technology would be suitable for searching for biomarkers, extinct life, potential habitats of extant life, and signatures of ancient climates on Mars; and for detecting biomarkers, prebiotic chemicals and habitats of life in the outer Solar System. It would be useful for prospecting for water on the Moon and asteroids, and characterizing its isotopic composition. Deployment on the Moon could provide ground truth to the recent remote measurements and help to uncover precious records of the early bombardment history of the inner Solar System buried at the shadowed poles, and elucidate the mechanism for the generation of near-surface water in the illuminated regions. The technology would also be useful for detecting other volatile molecules in planetary atmospheres and subsurface reservoirs, isotopic characterization of planetary materials, and searching for signatures of extinct life preserved in solid matrices.

Vasudev, Ram↗
NASA NTRS2005

Laboratory Evaluation and Application of Microwave Absorption Properties under Simulated Conditions for Planetary Atmospheres

Radio absorptivity data for planetary atmospheres obtained from spacecraft radio occultation experiments, entry probe radio signal absorption measurements, and earth- based or spacecraft-based radio astronomical (emission) observations can be used to infer abundances of microwave absorbing constituents in those atmospheres, as long as reliable information regarding the microwave absorbing properties of potential constituents is available. The use of theoretically-derived microwave absorption properties for such atmospheric constituents, or the use of laboratory measurements of such properties taken under environmental conditions that are significantly different than those of the planetary atmosphere being studied, often leads to significant misinterpretation of available opacity data. For example, new laboratory measurements completed recently by Mohammed and Steffes (2003 and 2004) under this grant (NAG5-12122,5/1/02-4/30/05), have shown that the millimeter-wavelength opacities from both gaseous phosphine (PH3) and gaseous ammonia ("3) under simulated conditions for the outer planets vary significantly from that predicted by theory over a wide range of temperatures and pressures. These results have directly impacted planning and scientific goals for study of Saturn's atmosphere with the Cassini Radio Science Experiment, as discussed below. The recognition of the need to make such laboratory measurements of simulated planetary atmospheres over a range of temperatures and pressures which correspond to the altitudes probed by both radio occultation experiments and radio astronomical observations, and over a range of frequencies which correspond to those used in both spacecraft entry probe and orbiter (or flyby) radio occultation experiments and radio astronomical observations, has led to the development of a facility at Georgia Tech which is capable of making such measurements. It has been the goal of this investigation to conduct such measurements and to apply the results to a wide range of planetary observations, both spacecraft and earth-based, in order to determine the identity and abundance profiles of constituents in those planetary atmospheres.

Steffes, Paul G.↗
NASA NTRSDate not supplied

Inertial Centrifugal-Based Pre-filter for Spacecraft Life Support Systems

The intrusion of planetary dust inside space vehicles on future Lunar missions may lead to performance compromises of the cabin air-filtration system. The evasive character of the fine planetary dust, in particular lunar dust, could enable the dust to make its way through the seals and barriers of the EVA hatches and become airborne in the cabin. This can result in performance and capacity overload of the high efficiency filter media and particle separation systems. Adequate pre-filtration can substantially reduce the load on the higher efficiency components leading to smaller dust loads during surge and nominal dust loading conditions, thereby protecting and extending the life of these components. A particle separation concept, based on centrifugal separation, is being investigated for its application as a pre-filter. The concept has previously been proposed for application in the aircraft engine industry, as means of capturing corrosive dust and salt deposits that may harm the engine. The technique has the advantages of being passive, integrable to HVAC and space vehicle architecture, and has the potential for high degree of particle separation with proper fluid dynamic design. Computational Fluid Dynamics (CFD) and particle tracing modeling were used to arrive at an initial design for rapid prototyping and testing. If feasible, the concept can be integrated to the Scroll Filter System which is being developed by NASA to address the filtration demands on long during spaceflight and surface missions. This paper will describe the modeling results of this concept.

Life Support Systems↗
NASA NTRSDate not supplied

Inertial Centrifugal-Based Pre-filter for Spacecraft Life Support Systems

The intrusion of planetary dust inside space vehicles on future Lunar missions may lead to performance compromises of the cabin air-filtration system. The evasive character of the fine planetary dust, in particular lunar dust, could enable the dust to make its way through the seals and barriers of the EVA hatches and become airborne in the cabin. This can result in performance and capacity overload of the high efficiency filter media and particle separation systems. Adequate pre-filtration can substantially reduce the load on the higher efficiency components leading to smaller dust loads during surge and nominal dust loading conditions, thereby protecting and extending the life of these components. A particle separation concept, based on centrifugal separation, is being investigated for its application as a pre-filter. The concept has previously been proposed for application in the aircraft engine industry, as means of capturing corrosive dust and salt deposits that may harm the engine. The technique has the advantages of being passive, integrable to HVAC and space vehicle architecture, and has the potential for high degree of particle separation with proper fluid dynamic design. Computational Fluid Dynamics (CFD) and particle tracing modeling were used to arrive at an initial design for rapid prototyping and testing. If feasible, the concept can be integrated to the Scroll Filter System which is being developed by NASA to address the filtration demands on long during spaceflight and surface missions. This paper will describe the modeling results of this concept.

Life Support Systems↗
NASA NTRS1985

Photographic catalog of selected planetary size comparisons

Photographs taken by NASA spacecraft, and cartographic products based on these photos, are used to illustrate size comparisons of the planets and moons of the solar system. Global views and prominent geographical features are depicted at the same scale, allowing size relationships to be studied visually.

Meszaros, S. P.↗
NASA NTRSDate not supplied

Large Vehicle Lunar Landing Surface Interaction and In-Situ Resource Based Risk Mitigation

A key capability required for the exploration of planetary bodies is the ability to land on the surface. Previous work performed by NASA and other institutions has primarily focused on landing small spacecraft on planetary surfaces and the associated small-to-medium thrusters required for the soft landing. In the case of human exploration—particularly the establishment of long duration exploration and habitation outposts—the ability to land large landers, such as the SpaceX Starship, is necessary. These larger landing systems require the use of more powerful engines, with higher temperature engine exhaust and higher landing loads. Understanding the excavation of material by the engines, as well as the potential for the landing legs to sink into the subsurface, is key in ensuring reliable and safe landings. A further improvement in landing reliability can be achieved by constructing landing/launchpads, especially with in-situ resources.

Landing Pad↗
NASA NTRS1983

Coherent infrared lidar mission and technology needs for measurements of transport and concentration of tropospheric trace species

The science justification and the feasibility of aircraft-based CO2 Doppler lidar measurements of transport between the free troposphere and the stratosphere (or planetary boundary layer) are discussed for a wide range of seasonal and geographic conditions. Ground-based coherent CO2 lidar aerosol scattering experiments using a stable ring resonator (about 50 mJ/pulse) CO2 laser with external injection locking are reported. Comparative studies of injection-locked CO2 laser unstable resonators and master oscillator power amplifiers are reported for future CO2 lidar missions with respect to requirements of pulse energy, duration/shape, frequency chirp, efficiency for heterodyne detection, and combined Doppler lidar and Differential Absorption Lidar missions.

Hess, R. V.↗
NASA NTRS1995

Some Recent Advances and Applications of Infrared Detector Technology at the Jet Propulsion Laboratory

The Jet Propulsion Laboratory has a long history in the development and application of infrared detector technology for the exploration of our planetary system. We will describe some recent applications of IR detector technology at JPL for ground based astronomy, the Earth Observing System, the Cassini Mission to Saturn, and the other proposed planetary missions. The infrared detector technologies to be discussed include single element, multiplexed linear and staring arrays, using a wide variety of infrared sensing materials including InSb, InGaAs, HgCdTe (PV and PC) and SiAs.

IR↗
NASA NTRS1991

Properties of planetary fluids at high pressures and temperatures

Observational data obtained by the Voyager space probes to the giant planets Jupiter, Saturn, Uranus, and Neptune have provided valuable information, which is used to refine the picture of the nature of the interiors of these planets. Major results from the Voyager missions include observations of substantial magnetic fields and improved models of internal density distributions. The goal is to obtain equations of state and electrical conductivity data for planetary gases (H2 and He) and the ices (H2O, CH4, and NH3, and their mixtures), which are considered to be the major constituents of the giant planets. These data are needed to test theoretical data bases used to construct models of the chemical composition of planetary interiors, models which are consistent with observables such as mass, diameter, gravitational moments, rotation rate, and magnetic field. The 100 GPa (1 Mbar) pressures and several 1000 K temperatures in the giant planets can be achieved in the lab by the shock compression of liquid specimens. Results are briefly examined.

Nellis, W. J.↗
NASA NTRS1998

Laboratory Evaluation and Application of Microwave Absorption Properties Under Simulated Conditions for Planetary Atmospheres

Radio absorptivity data for planetary atmospheres obtained from spacecraft radio occultation experiments, entry probe radio signal absorption measurements, and earth-based radio astronomical observations can be used to infer abundances of microwave absorbing constituents in those atmospheres, as long as reliable information regarding the microwave absorbing properties of potential constituents is available. The use of theoretically-derived microwave absorption properties for such atmospheric constituents, or using laboratory measurements of such properties taken under environmental conditions which are significantly different than those of the planetary atmosphere being studied, often leads to significant misinterpretation of available opacity data. For example, laboratory measurements completed recently by Kolodner and Steffes (ICARUS 132, pp. 151-169, March 1998, attached as Appendix A) under this grant (NAGS-4190), have shown that the opacity from gaseous H2SO4 under simulated Venus conditions is best described by a different formalism than was previously used. The recognition of the need to make such laboratory measurements of simulated planetary atmospheres over a range of temperatures and pressures which correspond to the altitudes probed by both spacecraft entry probe and orbiter radio occultation experiments and by radio astronomical observations, and over a range of frequencies which correspond to those used in such experiments, has led to the development of a facility at Georgia Tech which is capable of making such measurements. It has been the goal of this investigation to conduct such measurements and to apply the results to a wide range of planetary observations, both spacecraft and earth-based, in order to determine the identity and abundance profiles of constituents in those planetary atmospheres.

Steffes, Paul G.↗
NASA NTRSDate not supplied

Considerations for Health and Performance During Surface Extravehicular Activities

BACKGROUND: NASA’s objectives for expanding human presence beyond low Earth orbit will require Extravehicular Activities (EVAs) on lunar and planetary surfaces. Given the physiological and functional demands of conducting surface EVAs in a pressurized spacesuit in reduced gravity environments, there is a possibility that crew injury and compromised physiological and/or functional performance may present. OVERVIEW: Many human health and performance knowledge gaps exist in regards to exploration EVA that require characterization to ensure safety, reliability, and mission success. To address knowledge gaps, EVA simulations in Earth-based analog environments and/or spacesuit simulators can be utilized to provide valuable insights into task-based physiologic and metabolic costs, cognitive loads, and associated operational limitations to inform future mission concepts. Physical workloads approaching 60% of maximum metabolic rates and 85% age-predicted heart rate maxima; core body temperatures approaching 100o F; and subjective responses indicating limited spare cognitive capacity via Bedford scale have been observed during ground-based exploration EVA simulations in the NASA Active Response Gravity Offload Simulator (ARGOS) and Neutral Buoyancy Lab (NBL) during simulated planetary EVAs in pressurized suits. Further, ground-based EVA analogs vary in their ability to simulate planetary EVA and resulting physical workloads. DISCUSSION: Metabolic costs, thermal burdens, functional strength, and cognitive impacts have been and must continue to be assessed in ground-based analogs to fully characterize operational demands and crew readiness levels for exploration EVA. Considerations should be given to enabling a new concept of high-tempo surface EVA operations and associated work-rest intervals, understanding human health and performance impacts of evolving commercial suit designs and capabilities, and predictive modeling and decision support capabilities to enable safe and successful EVA operations.

EVA↗
NASA NTRS2024

Considerations for Health and Performance during Surface Extravehicular Activities

BACKGROUND: NASA’s objectives for expanding human presence beyond low Earth orbit will require Extravehicular Activities (EVAs) on lunar and planetary surfaces. Given the physiological and functional demands of conducting surface EVAs in a pressurized spacesuit in reduced gravity environments, there is a possibility that crew injury and compromised physiological and/or functional performance may present. OVERVIEW: Many human health and performance knowledge gaps exist in regards to exploration EVA that require characterization to ensure safety, reliability, and mission success. To address knowledge gaps, EVA simulations in Earth-based analog environments and/or spacesuit simulators can be utilized to provide valuable insights into task-based physiologic and metabolic costs, cognitive loads, and associated operational limitations to inform future mission concepts. Physical workloads approaching 60% of maximum metabolic rates and 85% age-predicted heart rate maxima; core body temperatures approaching 100° F; and subjective responses indicating limited spare cognitive capacity via Bedford scale have been observed during ground-based exploration EVA simulations in the NASA Active Response Gravity Offload Simulator (ARGOS) and Neutral Buoyancy Lab (NBL) during simulated planetary EVAs in pressurized suits. Further, ground-based EVA analogs vary in their ability to simulate planetary EVA and resulting physical workloads. DISCUSSION: Metabolic costs, thermal burdens, functional strength, and cognitive impacts have been and must continue to be assessed in ground-based analogs to fully characterize operational demands and crew readiness levels for exploration EVA. Considerations should be given to enabling a new concept of high-tempo surface EVA operations and associated work-rest intervals, understanding human health and performance impacts of evolving commercial suit designs and capabilities, and predictive modeling and decision support capabilities to enable safe and successful EVA operations.

P Estep↗
NASA NTRS2002

Laboratory Evaluation and Application of Microwave Absorption Properties under Simulated Conditions for Planetary Atmospheres

Radio absorptivity data for planetary atmospheres obtained from spacecraft radio occultation experiments, entry probe radio signal absorption measurements, and earth-based or spacecraft-based radio astronomical (emission) observations can be used to infer abundances of microwave absorbing constituents in those atmospheres, as long as reliable information regarding the microwave absorbing properties of potential constituents is available. The use of theoretically-derived microwave absorption properties for such atmospheric constituents, or the use of laboratory measurements of such properties taken under environmental conditions that are significantly different than those of the planetary atmosphere being studied, often leads to significant misinterpretation of available opacity data. Laboratory measurements have shown that the centimeter-wavelength opacity from gaseous phosphine (PH3) under simulated conditions for the outer planets far exceeds that predicted from theory over a wide range of temperatures and pressures. This fundamentally changed the resulting interpretation of Voyager radio occultation data at Saturn and Neptune. It also directly impacts planning and scientific goals for study of Saturn's atmosphere with the Cassini Radio Science Experiment and the Rossini RADAR instrument. The recognition of the need to make such laboratory measurements of simulated planetary atmospheres over a range of temperatures and pressures which correspond to the altitudes probed by both radio occultation experiments and radio astronomical observations, and over a range of frequencies which correspond to those used in both spacecraft entry probe and orbiter (or flyby) radio occultation experiments and radio astronomical observations, has led to the development of a facility at Georgia Tech which is capable of making such measurements. It has been the goal of this investigation to conduct such measurements and to apply the results to a wide range of planetary observations, both spacecraft- and earth-based, in order to determine the identity and abundance profiles of constituents in those planetary atmospheres,

Steffes, Paul G.↗
NASA NTRS1990

On planetary nebulae as sources of carbon dust: Infrared emission from planetary nebulae of the galactic halo

Planetary nebulae of the galactic disk are generally seen to emit a thermal continuum due to dust grains heated by stellar and nebular photons. This continuum typically peaks between 25 and 60 micron m, so that the total power emitted by the dust is sampled well by the broad-band measurements made by IRAS. Researchers examine here the characteristics of the infrared emission from the four planetary nebulae which are believed on the basis of their low overall metallicities to belong to the halo population. These nebulae are of particular interest because they are the most metal-poor ionized nebulae known in our Galaxy, and offer the opportunity to probe possible dependences of the dust properties on nebular composition. Researchers present fluxes extracted from co-addition of the IRAS data, as well as ground-based near infrared measurements. Each of the four halo objects, including the planetary nebula in the globular cluster M15, is detected in at least one infrared band. Researchers compare the estimated infrared excesses of these nebulae (IRE, the ratio of measured infrared power to the power available in the form of resonantly-trapped Lyman alpha photons) to those of disk planetary nebulae with similar densities but more normal abundances. Three of the halo planetaries have IRE values similar to those of the disk nebulae, despite the fact that their Fe- and Si-peak gas phase abundances are factors of 10 to 100 lower. However, these halo nebulae have normal or elevated C/H ratios, due to nuclear processing and mixing in their red giant progenitors. Unlike the other halo planetaries, DDDM1 is deficient in carbon as well as in the other light metals. This nebula has a substantially lower IRE than the other halo planetaries, and may be truly dust efficient. Researchers suggest that the deficiency is due to a lack of the raw material for producing carbon-based grains, and that the main bulk constituent of the dust in these planetary nebulae is carbon.

Dinerstein, Harriet L.↗
NASA NTRS2005

Pico Reentry Probes: Affordable Options for Reentry Measurements and Testing

It is generally very costly to perform in-space and atmospheric entry experiments. This paper presents a new platform - the Pico Reentry Probe (PREP) - that we believe will make targeted flight-tests and planetary atmospheric probe science missions considerably more affordable. Small, lightweight, self-contained, it is designed as a "launch and forget" system, suitable for experiments that require no ongoing communication with the ground. It contains a data recorder, battery, transmitter, and user-customized instrumentation. Data recorded during reentry or space operations is returned at end-of-mission via transmission to Iridium satellites (in the case of earth-based operations) or a similar orbiting communication system for planetary missions. This paper discusses possible applications of this concept for Earth and Martian atmospheric entry science. Two well-known heritage aerodynamic shapes are considered as candidates for PREP: the shape developed for the Planetary Atmospheric Experiment Test (PAET) and that for the Deep Space II Mars Probe.

Ailor, William H.↗
NASA NTRS1974

Submillimeter observations of planets

A new program of ground-based observations at submillimeter (about 400-micron) wavelengths has yielded observations of Mercury, Venus, Mars, Jupiter, and Saturn. We report here observations near planetary conjunctions, which have minimal corrections for atmospheric extinction: Mercury, 361 + or - 65 K; Venus, 231 + or - 35 K; and Saturn, 205 + or - 15 K (based upon the area of the planetary disk), using Jupiter (150 K) and Mars (220 K) as photometric standards. The Mercury observations show that the brightness temperature does not decrease at the submillimeter wavelengths, relative to observations at 3 mm; for Venus, however, the brightness temperature appears appreciably lower than at millimeter wavelengths. The results for Saturn indicate a strong and possibly optically thick contribution from the rings.

Hudson, H. S.↗