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At least 451 records · Page 25

Unveiling Clues from Spacecraft Missions to Comets and Asteroids through Impact Experiments

The Deep Impact Spacecraft mission was the first to boldly face the challenge of impacting the surface of a comet, 9P/Tempel 1, to investigate surface and subsurface 'pristine' materials. The Stardust mission to Comet 81P/Wild 2 brought back an exciting surprise: shocked minerals which were likely altered during the comet's lifetime. Signatures of shock in meteorites also suggest that the violent past of the solar system has left our small bodies with signatures of impacts and collisions. These results have led to the question: How have impacts affected the evolutionary path taken by comets and asteroids, and what signatures can be observed? A future planetary mission to a near-Earth asteroid is proposing to take the next steps toward understanding small bodies through impacts. The mission would combine an ESA led AIM (Asteroid Impact Mission) with a JHU/APL led DART (Double Asteroid Redirect Mission) spacecraft to rendezvous with binary near-Earth asteroid 65803 Didymus (1996 G2). DART would impact the smaller asteroid, 'Didymoon' while AIM would characterize the impact and the larger Didymus asteroid. With these missions in mind, a suite of experiments have been conducted at the Experimental Impact Laboratory (EIL) at NASA Johnson Space Center to investigate the effects that collisions may have on comets and asteroids. With the new capability of the vertical gun to cool targets in the chamber through the use of a cold jacket fed by liquid nitrogen, the effects of target temperature have been the focus of recent studies. Mg-rich forsterite and enstatite (orthopyroxene), diopside (monoclinic pyroxene) and magnesite (Mg-rich carbonate) were impacted. Target temperatures ranged from 25 deg to -100 deg, monitored by connecting thermocouples to the target container. Impacted targets were analyzed with a Fourier Transform Infrared Spectrometer (FTIR) and Transmission Electron Microscope (TEM). Here we present the evidence for impact-induced shock in the minerals through both spectra and TEM imaging and compare with unshocked samples.

Lederer, Susan M.↗

3-μm Spectroscopy of Phobos and Deimos

The origin of the Martian moons Phobos and Deimos is still not well understood and two scenarios have been proposed for their formation: in-situ and captured asteroid[1]. The in-situ scenario suggested that Phobos and Deimos were formed from Martian materials by co-accretion with Mars[2] or re-accretion of Mars (e.g.,[3],[4],[5]). The captured asteroid scenario proposed that Phobos and Deimos were formed from captured primitive materials originating from the outer solar system[6, 7]. Previous telescopic data have revealed significant information about Phobos’ and Deimos’ spectral properties [8,9,10,11]. Additionally, spacecraft and spec-trometers such as Observatoire pour la Mineralogie, L’Eau, Les Glaces et l’Activité (OMEGA) onboard Mars Express and the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) onboard Mars Reconnaissance Orbiter (MRO) collected visible to near-infrared imaging spectroscopic data of both Phobos and Deimos [12, 13,14,15]. Results from these investigations show that the two moons are moderately low albedo objects with no significant diagnostic absorptions of common ferrous minerals such as olivine and pyroxene. All these ground-and space-based spectroscopic studies of Phobos and Deimos included a spectral range that did not go beyond ~3.5 μm. Here we present spectra of Phobos and Deimos that cover the ~0.7-4 μmrange to search for signatures of hydrated minerals, organics, and carbonates.

D Takir↗

Deep Space Relay Terminals for Mars Superior Conjunction

The Sun periodically blocks direct communication between the Earth and Mars, creating a need for a relay when missions have a critical need for communication during these times. We examined several approaches based on optical or radio-frequency relays placed in deep space between the Earth and Mars, exploring multiple possible placements of relays, including periodic orbits in the Sun-Earth and Sun-Mars rotating frames, and eccentric, sun-centered orbits. L4 and L5 long-period orbits in the sun-Mars system provide suitable communications geometry continuously for very long durations. In such an orbit, a deep space relay terminal with two 50 cm optical telescopes and two 75 cm Ka-band dish antennas, along with associated receivers and transmitters, would be capable of supporting Mars superior conjunctions with an optical data rate of 28 to 44 Mbps for return links, and 30-36 Mbps in the forward direction. The relay should use efficient, low-noise optical detectors, such as appropriately cooled Avalanche Photo Diode or Superconducting Nanowire Single Photon Detectors, to achieve these data rates. The single relay discussed in this study might have additional value beyond communications, providing a synergistic platform for solar observation, solar wind observation, gravitational studies, the search for near-earth asteroids, or a navigational beacon.

Lau, Chi-Wung↗

Mass Spectrometers in Space!

Exploration of our solar system over several decades has benefitted greatly from the sensitive chemical analyses offered by spaceflight mass spectrometers. When dealing with an unknown environment, the broadband detection capabilities of mass analyzers have proven extremely valuable in determining the composition and thereby the basic nature of space environments, including the outer reaches of Earth s atmosphere, interplanetary space, the Moon, and the planets and their satellites. Numerous mass analyzer types, including quadrupole, monopole, sector, ion trap, and time-of-flight have been incorporated in flight instruments and delivered robotically to a variety of planetary environments. All such instruments went through a rigorous process of application-specific development, often including significant miniaturization, testing, and qualification for the space environment. Upcoming missions to Mars and opportunities for missions to Venus, Europa, Saturn, Titan, asteroids, and comets provide new challenges for flight mass spectrometers that push to state of the art in fundamental analytical technique. The Sample Analysis at Mars (SAM) investigation on the recently-launch Mars Science Laboratory (MSL) rover mission incorporates a quadrupole analyzer to support direct evolved gas as well as gas chromatograph-based analysis of martian rocks and atmosphere, seeking signs of a past or present habitable environment. A next-generation linear ion trap mass spectrometer, using both electron impact and laser ionization, is being incorporated into the Mars Organic Molecule Analyzer (MOMA) instrument, which will be flown to Mars in 2018. These and other mass spectrometers and mission concepts at various stages of development will be described.

Brinckerhoff, William B.↗

On-board Science Understanding: NASA Ames' Efforts

In the near future NASA intends to explore various regions of our solar system using robotic devices such as rovers, spacecraft, airplanes, and/or balloons. Such platforms will likely carry imaging devices, and a variety of analytical instruments intended to evaluate the chemical and mineralogical nature of the environment(s) that they encounter. Historically, mission operations have involved: (1) return of scientific data from the craft; (2) evaluation of the data by space scientists; (3) recommendations of the scientists regarding future mission activity; (4) commands for achieving these activities being transmitted to the craft; and (5) the activity being undertaken. This cycle is then repeated for the duration of the mission with command opportunities once or perhaps twice per day. In a rapidly changing environment, such as might be encountered by a rover traversing hundreds of meters a day or a spacecraft encountering an asteroid, this historical cycle is not amenable to rapid long range traverses, discovery of novelty, or rapid response to any unexpected situations. In addition to real-time response issues, the nature of imaging and/or spectroscopic devices are such that tremendous data volumes can be acquired, for example during a traverse. However, such data volumes can rapidly exceed on-board memory capabilities prior to the ability to transmit it to Earth. Additionally, the necessary communication band-widths are restrictive enough so that only a small portion of these data can actually be returned to Earth. Such scenarios clearly require the enabling of some crucial decisions to be made on-board by these robotic explorers. These decisions transcend the electromechanical control, health, and navigation issues associated with robotic operations. Instead they focus upon a long term goal of automating scientific discovery based upon data returned by sensors of the robot craft. Such an approach would eventually enable it to understand what is interesting because the data deviates from expectations generated by current theories/models of planetary processes that could have resulted in the observed data. Such interesting data and/or conclusions can then be selectively transmitted to Earth thus reducing memory and communications demands.

Roush, Ted L.↗

A search for stellar occultations by Uranus, Neptune, Pluto, and their satellites: 1990-1999

A search for occultations of stars by Uranus, Neptune, and Pluto between 1990 and 1999 was carried out by combining ephemeris information and star positions using very accurate occultation modeling software. Stars from both the Space Telescope Guide Catalog and photographic plates taken by Arnold Klemola at Lick Observatory were compared with planet positions from the JPL DE-130 ephemeris, with local modifications for Pluto and Charon. Some 666 possible occultations by the Uranian ring, 143 possible occultations by Neptune, and 40 possible occultations by Pluto and/or Charon were found among stars with visual magnitudes as faint as 16. Before the star positions could be obtained, the occultation prediction software was used to aid many observers in observing the occultation of 28 Sagitarii by Saturn in July 1989. As a test on other outer solar system objects, 17 possible occultations were found in a search of the Guide Star Catalog for occultations by 2060 Chiron, and interesting object between Saturn and Uranus which shows both cometary and asteroidal properties.

Mink, Douglas J.↗

Intercontinental Bistatic Radar Test Observation of Asteroid 1998 WT24

We describe the first intercontinental planetary radar test performed in Italy observing the near Earth asteroid (NEA) 33342 (1998 WT24) in December 2001 by means of the bistatic configurations Goldstone (California, USA)-Medicina (Italy) and Evpatoria (Ukraine)-Medicina. The experiment goal was to characterize the system for realtime radar follow-up observations of NEAs and artificial orbiting debris, in the framework of a feasibility study which aims at using the Sardinia Radio Telescope, at present under construction, also as a planetary radar facility. We report the preliminary results of the radar observations carried out by the IRA-CNR (Instituto di Radioastronomia - Consiglio Nazionale delle Ricerche) and the OATo (Osservatorio Astronomico di Torino) groups, aimed at exploring the scientific potentials of a new space radar program, using the existing facilities in Italy. The planetary radar technique is uniquely capable of investigating geometry and surface properties of various solar system objects, demonstrating advantages over the optical methods in its high spatial resolution and ability to obtain three-dimensional images. A single radar detection allows to obtain extremely accurate orbital elements, improving the instantaneous positional uncertainties by orders of magnitude with respect to an optically determined orbit. Radar is a powerful means to spatially resolve NEAs by measuring the distribution of the echo power in time delay (range) and Doppler frequency (line-of-sight velocity) with extreme precision in each coordinate, as it provides detailed information about the target physical properties like size, shape, rotation, near-surface bulk density and roughness and internal density distribution. The Medicina 32m antenna had been successfully used for the first time as the receiving part of a bistatic configuration during a test experiment (September 2001) held to check the capabilities of the entire data acquisition system. This test was possible thanks to the collaboration undertaken with the Evpatoria radar station, and consisted in the observation of the ETALON-1 low orbit satellite

Righini, S.↗

Common Warm Dust Temperatures Around Main Sequence Stars

We compare the properties of warm dust emission from a sample of main-sequence A-type stars (B8-A7) to those of dust around solar-type stars (F5-KO) with similar Spitzer Space Telescope Infrared Spectrograph/MIPS data and similar ages. Both samples include stars with sources with infrared spectral energy distributions that show evidence of multiple components. Over the range of stellar types considered, we obtain nearly the same characteristic dust temperatures (∼ 190 K and ∼60 K for the inner and outer dust components, respectively)-slightly above the ice evaporation temperature for the inner belts. The warm inner dust temperature is readily explained if populations of small grains are being released by sublimation of ice from icy planetesimals. Evaporation of low-eccentricity icy bodies at ∼ 150 K can deposit particles into an inner/warm belt, where the small grains are heated to dust Temperatures of -190 K. Alternatively, enhanced collisional processing of an asteroid belt-like system of parent planetesimals just interior to the snow line may account for the observed uniformity in dust temperature. The similarity in temperature of the warmer dust across our B8-KO stellar sample strongly suggests that dust-producing planetesimals are not found at similar radial locations around all stars, but that dust production is favored at a characteristic temperature horizon.

Morales, Farisa↗

Development of a High Performance, Low-Profile Translation Table with Wire Feedthrough

NEAScout, a 6U cubesat, will use an 85 sq m solar sail to travel to a near-earth asteroid for observation. Over the course of the 3-year mission, a combination of reaction wheels, cold gas reaction control system, and a slow rotisserie roll about the solar sail's normal axis were expected to handle attitude control and adjust for imperfections in the deployed sail. As the design for NEAScout matured, one of the critical design parameters, the offset in the center of mass and center of pressure (CP/CM offset), proved to be sub-optimal. After significant mission and control analysis, the CP/CM offset was addressed and a new subsystem was introduced to NEAScout. This system, called the Active Mass Translator (AMT), would reside near the geometric center of NEAScout and adjust the CM by moving one portion of the flight system relative to the other. The AMT was given limited design space-about 17 mm of the vehicle's assembly height-and was required to generate +/-10 cm by +/-5 cm translation to sub-millimeter accuracy. Furthermore, the design must accommodate a large wire bundle of small gage, single strand wire and coax cables fed through the center of the mechanism. The bend radius, bend resistance, and the exposure to deep space environment complicates the AMT design and operation and necessitated a unique design to mitigate risks of wire bundle damage, binding, and cold-welding during operation. This paper will outline the design constraints for the AMT, discuss the methods and reasoning for design, and identify the lessons learned through the design downselect process and breadboarding for designing low-profile translation stages with feedthrough capabilities.

Few, Alex↗

Nature of the Kirkwood gaps in the asteroid belt

It is demonstrated that the Kirkwood gaps are not merely regions of low asteroidal number density, but are regions in a-e-sin 1/2 I space where libration of some argument is possible. It is argued that neither the statistical nor the cosmogonic hypothesis of gap formation can account for these new observations. It is shown that the present distribution of asteroidal semimajor axes can be used to deduce the present semimajor axis of Jupiter to an accuracy of one part in five thousand. Thus, there has been very little change in the orbital period of Jupiter since the time of formation of the present gaps. This observation eliminates the possibility that the observed gaps were formed by resonance sweeping at the time of the dispersal of the accretion disk. It is concluded that the gaps have been formed by the gravitational action of Jupiter on individual asteroids and that gap formation has probably continued throughout the lifetime of the solar system.

Dermott, S. F.↗

Breakthrough Capability for UVOIR Space Astronomy: Reaching the Darkest Sky

We describe how availability of new solar electric propulsion (SEP) technology can substantially increase the science capability of space astronomy missions working within the near-UV to far-infrared (UVOIR) spectrum by making dark sky orbits accessible for the first time. We present two case studies in which SEP is used to enable a 700 kg Explorer-class and 7000 kg flagship-class observatory payload to reach an orbit beyond where the zodiacal dust limits observatory sensitivity. The resulting scientific performance advantage relative to a Sun-Earth L2 point (SEL2) orbit is presented and discussed. We find that making SEP available to astrophysics Explorers can enable this small payload program to rival the science performance of much larger long development-time systems. Similarly, we find that astrophysics utilization of high power SEP being developed for the Asteroid Redirect Robotics Mission (ARRM) can have a substantial impact on the sensitivity performance of heavier flagship-class astrophysics payloads such as the UVOIR successor to the James Webb Space Telescope.

Space↗

Structure and evolutionary history of the solar system. III.

Analysis of the plasma processes and the hydromagnetic aspects involved in the evolution of the solar system. In order to reduce the speculative element as far as possible, the present analysis tries to connect the cosmogonic processes as directly as possible to laboratory plasma physics and to space phenomena actually observed today. Models of the Laplacian type have been made obsolete by magnetohydrodynamics. Furthermore they are in conflict with observations. A new model is suggested. A plasma surrounding a rotating central body may attain a state of partial corotation which is determined by the balance between gravitation and the centrifugal force acting on a plasma in a dipole field. Condensation from a partially corotating plasma results in grains orbiting in ellipses with e = 1/3 and finally accreting to bodies at 2/3 of the central distance of the point of condensation. An application of the theory of the Saturnian rings and to the asteroidal belt shows that the fall-down ratio 2/3 (derived from the geometry of a dipole field) is essential for the understanding of their structure. The structure of the groups of planets and satellites is also discussed, but only in a preliminary way.

Alfven, H.↗

Coproduction of volatiles and metals from extraterrestrial materials

Two main efforts in support of the general goals of SERC/culpr are presented. Investigations of processes for the coproduction of metals from extra-terrestrial materials in conjunction with plausible schemes for oxygen extraction continue. The principal emphasis was on the extraction and purification of iron from the ilmenite reduction process for oxygen, from the cathode metal deposits made in the magma electrolysis process for oxygen, and from native ferrous metal alloys on the moon and asteroids. All work on the separation and purification of ferrous metals was focussed upon the gaseous carbonyl process, a scheme that involves only temperatures attainable by passive thermal control. The exploration of a variety of schemes was initiated, involving the use of several different propulsion options and both propulsive and aerobraking capture at earth, for return of extraterrestrial resources to earth orbits. In addition, the search for new opportunities in space resource utilization continues. Examples include the continuation of work underway on: (1) the feasibility of locating solar power satellites in highly eccentric earth orbit; (2) the energetics of extracting the potential clean fusion fuel He-3 from the atmosphere for return to earth; and (3) the utility of a nuclear steam rocket (using non-terrestrial water as the working fluid) for transportation in the inner solar system.

Lewis, John S.↗

Toolbox for Research and Exploration (TREX): Investigations of Fine-Grained Materials on Small Bodies

The Toolbox for Research and Exploration (TREX) is a NASA SSERVI (Solar System Exploration Research Virtual Institute) node. TREX (trex.psi.edu) aims to decrease risk to future missions, specifically to the Moon, the Martian moons, and near- Earth asteroids, by improving mission success and assuring the safety of astronauts, their instruments, and spacecraft. TREX studies will focus on characteristics of the fine grains that cover the surfaces of these target bodies - their spectral characteristics and the potential resources (such as H2O) they may harbor. TREX studies are organized into four Themes (Laboratory- Studies, Moon-Studies, Small-Bodies Studies, and Field-Work). In this presentation, we focus on the work targeted by the Small-Bodies Theme. The Small-Bodies' Theme delves into several topics, many which overlap or are synergistic with the other TREX Themes. The main topics include photometry, spectral modeling, laboratory simulations of space weathering processes relevant to asteroids, the assembly of an asteroid regolith database, the dichotomy between nuclear and reflectance spectroscopy, and the dynamical evolution of asteroids and the implications for the retention of volatiles.

Domingue, D. L.↗

ISECG Mission Scenarios and Their Role in Informing Next Steps for Human Exploration Beyond Low Earth Orbit

The International Space Exploration Coordination Group (ISECG) was established in response to The Global Exploration Strategy (GES): The Framework for Coordination developed by fourteen space agencies* and released in May 2007. This GES Framework Document recognizes that preparing for human space exploration is a stepwise process, starting with basic knowledge and culminating in a sustained human presence in deep space. ISECG has developed several optional global exploration mission scenarios enabling the phased transition from human operations in Low Earth Orbit (LEO) and utilization of the International Space Station (ISS) to human missions beyond LEO leading ultimately to human missions to cis-lunar space, the Moon, Near Earth Asteroids, Mars and its environs. Mission scenarios provide the opportunity for judging various exploration approaches in a manner consistent with agreed international goals and strategies. Each ISECG notional mission scenario reflects a series of coordinated human and robotic exploration missions over a 25-year horizon. Mission scenarios are intended to provide insights into next steps for agency investments, following on the success of the ISS. They also provide a framework for advancing the definition of Design Reference Missions (DRMs) and the concepts for capabilities contained within. Each of the human missions contained in the scenarios has been characterized by a DRM which is a top level definition of mission sequence and the capabilities needed to execute that mission. While DRMs are generally destination focused, they will comprise capabilities which are reused or evolved from capabilities used at other destinations. In this way, an evolutionary approach to developing a robust set of capabilities to sustainably explore our solar system is defined. Agencies also recognize that jointly planning for our next steps, building on the accomplishments of ISS, is important to ensuring the robustness and sustainability of any human exploration plan. Developing a shared long-term vision is important, but agencies recognize this is an evolutionary process and requires consideration of many strategic factors. Strategic factors such as the implications of an emerging commercial space industry in LEO, the opportunity provided by extending ISS lifetime to at least 2020, and the importance of defining a plan which is sustainable in light of inevitable domestic policy shifts are timely for agency consideration.

Culbert, Christopher J.↗

Ion Engine and Hall Thruster Development at the NASA Glenn Research Center

NASA's Glenn Research Center has been selected to lead development of NASA's Evolutionary Xenon Thruster (NEXT) system. The central feature of the NEXT system is an electric propulsion thruster (EPT) that inherits the knowledge gained through the NSTAR thruster that successfully propelled Deep Space 1 to asteroid Braille and comet Borrelly, while significantly increasing the thruster power level and making improvements in performance parameters associated with NSTAR. The EPT concept under development has a 40 cm beam diameter, twice the effective area of the Deep-Space 1 thruster, while maintaining a relatively-small volume. It incorporates mechanical features and operating conditions to maximize the design heritage established by the flight NSTAR 30 cm engine, while incorporating new technology where warranted to extend the power and throughput capability. The NASA Hall thruster program currently supports a number of tasks related to high power thruster development for a number of customers including the Energetics Program (formerly called the Space-based Program), the Space Solar Power Program, and the In-space Propulsion Program. In program year 2002, two tasks were central to the NASA Hall thruster program: 1.) the development of a laboratory Hall thruster capable of providing high thrust at high power; 2.) investigations into operation of Hall thrusters at high specific impulse. In addition to these two primary thruster development activities, there are a number of other on-going activities supported by the NASA Hall thruster program, These additional activities are related to issues such as thruster lifetime and spacecraft integration.

Domonkos, Matthew T.↗

The Foreign Clast Populations of Anomalous Polymict Urelite Almahata Sitta (Asteroid 2008 TC(sub3) and Typical Polymict Ureilites: Implications for Asteroid-Meteorite Connections

Almahata Sitta (AhS) is the first meteorite to originate from an asteroid (2008 TC3) that had been studied in space before it hit Earth [1,2]. It is also unique because the fallen fragments comprise a variety of types: approximately 69% ureilites (achondrites) and 31% chondrites [3]. Two models have been proposed for the origin 2008 TC3: 1) an accretionary model [3,4]; or 2) a regolith model [5,6]. Typical polymict ureilites are interpreted to represent regolith, and contain a few % foreign clasts [7,8]. The most common are dark (CC matrix-like) clasts similar to those in many meteoritic breccias [9]. A variety of other chondrites, as well as achondrites (angrites), have also been reported [7,9,10]. We have been working to determine the full diversity of these clasts [10-13] for comparison with AhS. We discuss implications for mixing of materials in the early solar system and the origin of 2008 TC3.

Goodrich, C. A.↗

Concept designs for NASA's Solar Electric Propulsion Technology Demonstration Mission

Multiple Solar Electric Propulsion Technology Demonstration Mission were developed to assess vehicle performance and estimated mission cost. Concepts ranged from a 10,000 kilogram spacecraft capable of delivering 4000 kilogram of payload to one of the Earth Moon Lagrange points in support of future human-crewed outposts to a 180 kilogram spacecraft capable of performing an asteroid rendezvous mission after launched to a geostationary transfer orbit as a secondary payload. Low-cost and maximum Delta-V capability variants of a spacecraft concept based on utilizing a secondary payload adapter as the primary bus structure were developed as were concepts designed to be co-manifested with another spacecraft on a single launch vehicle. Each of the Solar Electric Propulsion Technology Demonstration Mission concepts developed included an estimated spacecraft cost. These data suggest estimated spacecraft costs of $200 million - $300 million if 30 kilowatt-class solar arrays and the corresponding electric propulsion system currently under development are used as the basis for sizing the mission concept regardless of launch vehicle costs. The most affordable mission concept developed based on subscale variants of the advanced solar arrays and electric propulsion technology currently under development by the NASA Space Technology Mission Directorate has an estimated cost of $50M and could provide a Delta-V capability comparable to much larger spacecraft concepts.

solar electric propulsion↗