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All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Assessment of DSN Communication Coverage for Space Missions to Potentially Hazardous Asteroids

A communication coverage gap exists for Deep Space Network (DSN) antennas. This communication coverage gap is on the southern hemisphere, centered at approximate latitude of -47deg and longitude of -45deg. The area of this communication gap varies depending on the altitude from the Earth s surface. There are no current planetary space missions that fall within the DSN communication gap because planetary bodies in the Solar system lie near the ecliptic plane. However, some asteroids orbits are not confined to the ecliptic plane. In recent years, Potentially Hazardous Asteroids (PHAs) have passed within 100,000 km of the Earth. NASA s future space exploration goals include a manned mission to asteroids. It is important to ensure reliable and redundant communication coverage/capabilities for manned space missions to dangerous asteroids that make a sequence of close Earth encounters. In this paper, we will describe simulations performed to determine whether near-Earth objects (NEO) that have been classified as PHAs fall within the DSN communication coverage gap. In the study, we reviewed literature for a number of PHAs, generated binary ephemeris for selected PHAs using JPL s HORIZONS tool, and created their trajectories using Satellite Took Kit (STK). The results show that some of the PHAs fall within DSN communication coverage gap. This paper presents the simulation results and our analyses

Kegege, Obadiah↗
NASA NTRS2012

Environmental Controls and Life Support System Design for a Space Exploration Vehicle

Engineers at Johnson Space Center (JSC) are developing an Environmental Control and Life Support System (ECLSS) design for the Space Exploration Vehicle (SEV). The SEV will aid to expand the human exploration envelope for Geostationary Transfer Orbit (GEO), Near Earth Object (NEO), or planetary missions by using pressurized surface exploration vehicles. The SEV, formerly known as the Lunar Electric Rover (LER), will be an evolutionary design starting as a ground test prototype where technologies for various systems will be tested and evolve into a flight vehicle. This paper will discuss the current SEV ECLSS design, any work contributed toward the development of the ECLSS design, and the plan to advance the ECLSS design based on the SEV vehicle and system needs.

Stambaugh, Imelda C.↗
NASA NTRS2012

Some Anticipated Science Results from "Local" Martian Sampling Site(s)

Current planning for return of a surface sample of Mars planned. Scientific aims and more detailed objectives relating to (a) past/extant life, (b) surface processes and interactions, (c) planetary evolution, and (d) human exploration are summarized in the Mars Exploration Program Analysis Group (MPEAG) document. Here we consider how these aims and objectives might be addressed by samples from individual "local" area(s) (diameter < approx 1 km) based on experience with analyzing subsamples of Martian meteorites.

Nyquist, L. E.↗
NASA NTRS2010

Emulating an Optical Planetary Access Link with an Aircraft

Video imagery was streamed from the ground to an aircraft using a free-space laser communication link. The link operated at 270 Mb/s over slant ranges of 5-9 km in day and night time background conditions. The experiment was designed to demonstrate autonomous link acquisition and served as a first proof-of-concept for a planetary access link between a surface asset and an orbiter at Mars. System parameters monitored during the link demonstration including acquisition and tracking and communication performance are discussed.

Ground-to-Aircraft↗
NASA NTRS2016

The Formation of Nucleobases from the Irradiation of Purine in Astophysical Ices and Comparisons with Meteorites.

N-heterocycles have been identified in meteorites and their extraterrestrial origins are suggested by isotopic ratio measurements. Although small N- heterocycles have not been detected in the interstellar medium (ISM), recent experiments in our lab have shown that the irradiation of the aromatic molecules like benzene (C6H6) and naphthalene (C10H8) in mixed molecular ices leads to the formation of O- and N-heterocyclic molecules. Among the class of N-heterocycles are the nucleobases, which are of astrobiological interest because they are the information bearing units of DNA and RNA. Nucleobases have been detected in meteorites [3-5], with isotopic signatures that are also consistent with an extraterrestrial origin. Three of the biologically relevant nucleobases (uracil, cytosine, and guanine) have a pyrimidine core structure while the remaining two (adenine and guanine) possess a purine core. Previous experiments in our lab have demonstrated that all of the bio-logical nucleobases (and numerous other molecules) with a pyrimidine core structure can be produced by irradiating pyrimidine in mixed molecular ices of several compositions [6-8]. In this work, we study the formation of purine-based molecules, including the nucleobases adenine, and guanine, from the ultraviolet (UV) irradiation of purine in ices consisting mixtures of H2O and NH3 at low temperature. The experiments are designed to simulate the astrophysical conditions under which these species may be formed in dense molecular clouds, protoplanetary disks, or on the surfaces of icy bodies in planetary systems.

Astrochemistry↗
NASA NTRS2016

Design and Analysis of Map Relative Localization for Access to Hazardous Landing Sites on Mars

Human and robotic planetary lander missions require accurate surface relative position knowledge to land near science targets or next to pre-deployed assets. In the absence of GPS, accurate position estimates can be obtained by automatically matching sensor data collected during descent to an on-board map. The Lander Vision System (LVS) that is being developed for Mars landing applications generates landmark matches in descent imagery and combines these with inertial data to estimate vehicle position, velocity and attitude. This paper describes recent LVS design work focused on making the map relative localization algorithms robust to challenging environmental conditions like bland terrain, appearance differences between the map and image and initial input state errors. Improved results are shown using data from a recent LVS field test campaign. This paper also fills a gap in analysis to date by assessing the performance of the LVS with data sets containing significant vertical motion including a complete data set from the Mars Science Laboratory mission, a Mars landing simulation, and field test data taken over multiple altitudes above the same scene. Accurate and robust performance is achieved for all data sets indicating that vertical motion does not play a significant role in position estimation performance.

Lander Vision System↗
NASA NTRS2019

Dawn's final mission at Ceres: navigation and mission design experience

On Oct. 31st, 2018, the Dawn spacecraft completed its space journey covering more than 11 years including exploration of Vesta and Ceres, two protoplanets in the main asteroid belt. After successfully completing its prime mission at the dwarf planet Ceres, the Dawn mission was extended twice to pursue new scientific objectives. The second extended mission at Ceres, and the final mission for Dawn, presented a series of challenges that were new to the experienced and accomplished Dawn navigation team. This paper discusses mission design and navigational experiences and challenges during Dawn’s final transfer and orbit at Ceres. Topics include reference orbit design of the final science orbit, mission design and planning for the transfer, periapsis targeting over a surface feature, and analysis for planetary protection requirements.

Karimi, Reza↗
NASA NTRS2015

Simplified Abrasion Test Methodology for Candidate EVA Glove Lay-Ups

During the Apollo Program, space suit outer‐layer fabrics were badly abraded after performing just a few extravehicular activities (EVAs). For example, the Apollo 12 commander reported abrasive wear on the boots that penetrated the outer‐layer fabric into the thermal protection layers after less than 8 hrs of surface operations. Current plans for the exploration planetary space suits require the space suits to support hundreds of hours of EVA on a lunar or Martian surface, creating a challenge for space suit designers to utilize materials advances made over the last 40 years and improve on the space suit fabrics used in the Apollo Program. Over the past 25 years the NASA Johnson Space Center Crew and Thermal Systems Division has focused on tumble testing as means of simulating wear on the outer layer of the space suit fabric. Most recently, in 2009, testing was performed on 4 different candidate outer layers to gather baseline data for future use in design of planetary space suit outer layers. In support of the High Performance EVA Glove Element of the Next Generation Life Support Project, testing a new configuration was recently attempted in which require 10% of the fabric per replicate of that need in 2009. The smaller fabric samples allowed for reduced per sample cost and flexibility to test small samples from manufacturers without the overhead to have a production run completed. Data collected from this iteration was compared to that taken in 2009 to validate the new test method. In addition the method also evaluated the fabrics and fabric layups used in a prototype thermal micrometeoroid garment (TMG) developed for EVA gloves under the NASA High Performance EVA Glove Project. This paper provides a review of previous abrasion studies on space suit fabrics, details methodologies used for abrasion testing in this particular study, results of the validation study, and results of the TMG testing.

Rabel, Emily↗
NASA NTRS1972

Problems affecting the fidelity of pressure measuring instruments for planetary probes

Determination is made of the nature and magnitude of surface-related effects that cause errors in pressure measuring instruments, with special reference being made to instruments intended for use in planetary probes. The interaction of gases with clean surfaces of metals likely to be used as gage construction materials was studied. Special emphasis was placed on the adsorption, chemical reaction, and electron-induced desorption processes. The results indicated that all metals tested were subject to surface processes which would degrade gage fidelity. It was also found, however, that the formation of inert adsorbed layers on these metal surfaces, such as carbon on platinum, greatly reduced or eliminated these effects. This process, combined with a system design which avoids contact between reactive gases and hot filaments, appears to offer the most promising solution to the gage fidelity problem.

Hudson, J. B.↗
DOE OSTI2014

Structure and dynamics of cold water super-Earths: the case of occluded CH{sub 4} and its outgassing

In this work, we study the transport of methane in the external water envelopes surrounding water-rich super-Earths. We investigate the influence of methane on the thermodynamics and mechanics of the water mantle. We find that including methane in the water matrix introduces a new phase (filled ice), resulting in hotter planetary interiors. This effect renders the super-ionic and reticulating phases accessible to the lower ice mantle of relatively low-mass planets (∼5 M{sub E} ) lacking a H/He atmosphere. We model the thermal and structural profile of the planetary crust and discuss five possible crustal regimes which depend on the surface temperature and heat flux. We demonstrate that the planetary crust can be conductive throughout or partly confined to the dissociation curve of methane clathrate hydrate. The formation of methane clathrate in the subsurface is shown to inhibit the formation of a subterranean ocean. This effect results in increased stresses on the lithosphere, making modes of ice plate tectonics possible. The dynamic character of the tectonic plates is analyzed and the ability of this tectonic mode to cool the planet is estimated. The icy tectonic plates are found to be faster than those on a silicate super-Earth. A mid-layer of low viscosity is found to exist between the lithosphere and the lower mantle. Its existence results in a large difference between ice mantle overturn timescales and resurfacing timescales. Resurfacing timescales are found to be 1 Ma for fast plates and 100 Ma for sluggish plates, depending on the viscosity profile and ice mass fraction. Melting beneath spreading centers is required in order to account for the planetary radiogenic heating. The melt fraction is quantified for the various tectonic solutions explored, ranging from a few percent for the fast and thin plates to total melting of the upwelled material for the thick and sluggish plates. Ice mantle dynamics is found to be important for assessing the composition of the atmosphere. We propose a mechanism for methane release into the atmosphere, where freshly exposed reservoirs of methane clathrate hydrate at the ridge dissociate under surface conditions. We formulate the relation between the outgassing flux and the tectonic mode dynamical characteristics. We give numerical estimates for the global outgassing rate of methane into the atmosphere. We find, for example, that for a 2 M{sub E} planet outgassing can release 10{sup 27}-10{sup 29} molecules s{sup –1} of methane to the atmosphere. We suggest a qualitative explanation for how the same outgassing mechanism may result in either a stable or a runaway volatile release, depending on the specifics of a given planet. Finally, we integrate the global outgassing rate for a few cases and quantify how the surface atmospheric pressure of methane evolves over time. We find that methane is likely an important constituent of water planets' atmospheres.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1987

Source-surface model of the magnetosphere

A new concept for modeling a planetary magnetosphere is implemented by juxtaposing the sunward portion of the magnetosphere (in which the magnetic field is expressed formally as an analytical expansion) and the tail region (in which field lines are constructed geometrically). The expansion coefficients for the sunward region are determined by means of a variational principle, according to which a user-specified linear combination of the mean-square normal component of the magnetic field on the prescribed magnetopause and the mean-square tangential component of the magnetic field on the innermost cross-magnetospheric surface normal to the tail field lines must be minimized. The contour of the vanishing normal component of the magnetic field on this latter surface corresponds to the inner edge of the neutral sheet in the planetary magnetotail. In its present form, the source-surface model accommodates an arbitrary angle of incidence between the solar-wind velocity and the planetary magnetic-dipole moment.

Schulz, Michael↗
NASA NTRS2005

Astrobiological and Geological Implications of Convective Transport in Icy Outer Planet Satellites

The oceans of large icy outer planet satellites are prime targets in the search for extraterrestrial life in our solar system. The goal of our project has been to develop models of ice convection in order to understand convection as an astrobiologically relevant transport mechanism within icy satellites, especially Europa. These models provide valuable constraints on modes of surface deformation and thus the implications of satellite surface geology for astrobiology, and for planetary protection. Over the term of this project, significant progress has been made in three areas: (1) the initiation of convection in large icy satellites, which we find probably requires tidal heating; (2) the relationship of surface features on Europa to internal ice convection, including the likely role of low-melting-temperature impurities; and (3) the effectiveness of convection as an agent of icy satellite surface-ocean material exchange, which seems most plausible if tidal heating, compositional buoyancy, and solid-state convection work in combination. Descriptions of associated publications include: 3 published papers (including contributions to 1 review chapter), 1 manuscript in revision, 1 manuscript in preparation (currently being completed under separate funding), and 1 published popular article. A myriad of conference abstracts have also been published, and only those from the past year are listed.

Pappalardo, Robert T.↗
DOE OSTI2017

Estimating the Magnetic Field Strength in Hot Jupiters

A large fraction of known Jupiter-like exoplanets are inflated as compared to Jupiter. These “hot” Jupiters orbit close to their parent star and are bombarded with intense starlight. Many theories have been proposed to explain their radius inflation and several suggest that a small fraction of the incident starlight is injected into the planetary interior, which helps to puff up the planet. How will such energy injection affect the planetary dynamo? In this Letter, we estimate the surface magnetic field strength of hot Jupiters using scaling arguments that relate energy available in planetary interiors to the dynamo-generated magnetic fields. We find that if we take into account the energy injected in the planetary interior that is sufficient to inflate hot Jupiters to observed radii, then the resulting dynamo should be able generate magnetic fields that are more than an order of magnitude stronger than the Jovian values. Our analysis highlights the potential fundamental role of the stellar light in setting the field strength in hot Jupiters.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1988

Lunar surface magnetic field concentrations antipodal to young large impact basins

Planetary electron reflection magnetometry data of the Apollo 15 and 16 subsatellites indicate the presence of major regions of strong surface magnetic fields near the antipodes of four large, young, ringed impact basins. While mechanisms yielding surface magnetic field concentrations antipodal to impact basins are not yet clear, the present results' indicated period of strong lunar magnetic fields, at between about 3.85 and 3.6 aeons, is consistent with lunar paleomagnetic sample data. The origin of the strong surface magnetic fields is discussed.

Lin, R. P.↗
NASA NTRS2012

Site Tamper and Material Plow Tool - STAMP

A non-actuated tool has been developed for preparing regolith for in situ measurement by smoothing uneven surfaces and excavating fresher subsurface material for planetary exploration. The STAMP tool contains two tools to prepare regolith for in situ measurement: a tamper to smooth uneven surfaces, and a blade to excavate fresher subsurface material.

Aisen, Norman M.↗
NASA NTRS2017

Exploring the Largest Mass Fraction of the Solar System: the Case for Planetary Interiors

Why explore planetary interiors: The typical image that comes to mind for planetary science is that of a planet surface. And while surface data drive our exploration of evolved geologic processes, it is the interiors of planets that hold the key to planetary origins via accretionary and early differentiation processes. It is that initial setting of the bulk planet composition that sets the stage for all geologic processes that follow. But nearly all of the mass of planets is inaccessible to direct examination, making experimentation an absolute necessity for full planetary exploration.

Danielson, L. R.↗
NASA NTRS1998

Reflectance Spectroscopy and Lunar Sample Science: Finally a Marriage After Far Too Long an Engagement

Inferences about the igneous and impact evolution of planetary bodies are based upon spectral remote sensing of their surfaces. However, it is not the rocks of a body that are seen by the remote sensing, but rather the regolith, that may contain small pieces of rock but also many other phases as well. Indeed, recent flybys of objects even as small as asteroid Ida have shown that these objects are covered by a regolith. Thus, spectral properties cannot be directly converted into information about the igneous history of the object. It is imperative to fully understand the nature of the regolith, particularly its finer fraction termed "soil," to appreciate the possible effects of "space weathering" on the reflectance spectra. We have initiated a study of our nearest, regolith-bearing body, the Moon, as "ground truth" for further probes of planetary and asteroidal surfaces. the foundation for remote chemical and mineralogical analyses lies in the physics underlying optical absorption and the linking of spectral properties of materials measured in the laboratory to well understood mineral species and their mixtures. From this statement, it is obvious that there should be a thorough integration of the material science of lunar rocks and soils with the remote-sensing observations. That is, the lunar samples returned by the Apollo missions provide a direct means for evaluation of spectral characteristics of the Moon. However, this marriage of the remote-sensing and lunar sample communities has suffered from a prolonged unconsummated betrothal, nurtured by an obvious complacency by both parties. To make more direct and quantitative links between soil chemistry/mineralogy and spectral properties, we have initiated a program to (1) obtain accurate characterization of the petrography of lunar soils (in terms relevant to remote analyses), coupled with (2) measurement of precise reflectance spectra, with testing and use of appropriate analytical tools that identify and characterize individual mineral and glass components. It is the finest-sized fractions of the bulk lunar soil that dominate the observed spectral signatures.

Taylor, Lawrence A.↗

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