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NASA NTRS2005

Characterizing the Early Impact Bombardment

The early bombardment revealed in the larger impact craters and basins on the moon was a major planetary process that affected all bodies in the inner solar system, including the Earth and Mars. Understanding the nature and timing of this bombardment is a fundamental planetary problem. The surface density of lunar impact craters within a given size range on a given lunar surface is a measure of the age of that surface relative to other lunar surfaces. When crater densities are combined with absolute radiometric ages determined on lunar rocks returned to Earth, the flux of large lunar impactors through time can be estimated. These studies suggest that the flux of impactors producing craters greater than 1 km in diameter has been approximately constant over the past approx. 3 Gyr. However, prior to 3.0 - 3.5 Gyr the impactor flux was much larger and defines an early bombardment period. Unfortunately, no lunar surface feature older than approx. 4 Gyr is accurately dated, and the surface density of craters are saturated in most of the lunar highlands. This means that such data cannot define the impactor flux between lunar formation and approx. 4 Gyr ago.

Bogard, Donald D.↗
NASA NTRS2007

NASA Tech Briefs, March 2007

Topics include: Advanced Systems for Monitoring Underwater Sounds; Wireless Data-Acquisition System for Testing Rocket Engines; Processing Raw HST Data With Up-to-Date Calibration Data; Mobile Collection and Automated Interpretation of EEG Data; System for Secure Integration of Aviation Data; Servomotor and Controller Having Large Dynamic Range; Digital Multicasting of Multiple Audio Streams; Translator for Optimizing Fluid-Handling Components; AIRSAR Web-Based Data Processing; Pattern Matcher for Trees Constructed From Lists; Reducing a Knowledge-Base Search Space When Data Are Missing; Ground-Based Correction of Remote-Sensing Spectral Imagery; State-Chart Autocoder; Pointing History Engine for the Spitzer Space Telescope; Low-Friction, High-Stiffness Joint for Uniaxial Load Cell; Magnet-Based System for Docking of Miniature Spacecraft; Electromechanically Actuated Valve for Controlling Flow Rate; Plumbing Fixture for a Microfluidic Cartridge; Camera Mount for a Head-Up Display; Core-Cutoff Tool; Recirculation of Laser Power in an Atomic Fountain; Simplified Generation of High-Angular-Momentum Light Beams; Imaging Spectrometer on a Chip; Interferometric Quantum-Nondemolition Single-Photon Detectors; Ring-Down Spectroscopy for Characterizing a CW Raman Laser; Complex Type-II Interband Cascade MQW Photodetectors; Single-Point Access to Data Distributed on Many Processors; Estimating Dust and Water Ice Content of the Martian Atmosphere From THEMIS Data; Computing a Stability Spectrum by Use of the HHT; Theoretical Studies of Routes to Synthesis of Tetrahedral N4; Estimation Filter for Alignment of the Spitzer Space Telescope; Antenna for Measuring Electric Fields Within the Inner Heliosphere; Improved High-Voltage Gas Isolator for Ion Thruster; and Hybrid Mobile Communication Networks for Planetary Exploration.

Source record↗
NASA NTRS2012

Laboratory Studies of Charging Properties of Dust Grains in Astrophysical/Planetary Environments

Dust grains in various astrophysical environments are generally charged electrostatically by photoelectric emissions with UV/X-ray radiation, as well as by electron/ion impact. Knowledge of physical and optical properties of individual dust grains is required for understanding of the physical and dynamical processes in space environments and the role of dust in formation of stellar and planetary systems. In this paper we focus on charging of individual micron/submicron dust grains by processes that include: (a) UV photoelectric emissions involving incident photon energies higher than the work function of the material and b) electron impact, where low energy electrons are scattered or stick to the dust grains, thereby charging the dust grains negatively, and at sufficiently high energies the incident electrons penetrate the grain leading to excitation and emission of electrons referred to as secondary electron emission (SEE). It is well accepted that the charging properties of individual micron/submicron size dust grains are expected to be substantially different from the bulk materials. However, no viable models for calculation of the charging properties of individual micron size dust grains are available at the present time. Therefore, the photoelectric yields, and secondary electron emission yields of micron-size dust grains have to be obtained by experimental methods. Currently, very limited experimental data are available for charging of individual micron-size dust grains. Our experimental results, obtained on individual, micron-size dust grains levitated in an electrodynamic balance facility (at NASA-MSFC), show that: (1) The measured photoelectric yields are substantially higher than the bulk values given in the literature and indicate a particle size dependence with larger particles having order-of-magnitude higher values than for submicron-size grains; (2) dust charging by low energy electron impact is a complex process. Also, our measurements indicate that the electron impact may lead to charging or discharging of dust grains depending upon the grain size, surface potential, electron energy, electron flux, grain composition, and configuration (e.g. Abbas et al, 2010). Laboratory measurements on charging of analogs of the interstellar dust as well as Apollo 11 dust grains conducted at the NASA-MSFC Dusty Plasma Lab. are presented here

Tankosic, D.↗
NASA NTRS2015

NEA Scout and Lunar Flashlight: Two NearTerm Interplanetary CubeSat Missions

NASA is developing two small satellite missions as part of the Advanced Exploration Systems (AES) Program, both of which will use a solar sail to enable their scientific objectives. Solar sails reflect sunlight from a large, mirror‐like sail made of a lightweight, highly reflective material to provide thrust. This continuous photon pressure provides propellantless thrust, allowing for very high delta V maneuvers in space. Lunar Flashlight, managed by the NASA Jet Propulsion Laboratory, will search for and map volatiles in permanently shadowed lunar craters using a solar sail as a gigantic mirror to steer sunlight into them, then examine the reflected light with a spectrometer. The Lunar Flashlight spacecraft will also use the solar sail to maneuver into a lunar polar orbit. The mission will demonstrate a low‐cost capability to explore, locate and estimate the size and composition of ice deposits on the Moon. The Near Earth Asteroid (NEA) Scout mission, managed by the NASA Marshall Space Flight Center will survey and image a Near Earth Asteroid for possible future human exploration using a smallsat propelled by a solar sail. Detections of NEAs are expected to grow in the near future, offering increasing target opportunities. Obtaining and analyzing relevant data about these bodies via robotic precursors before committing a crew to visit them is essential. The NEA Scout spacecraft is nearly identical to the one being developed for Lunar Flashlight, with the science instrument package being the primary difference. The NEA Scout solar sail will provide the primary propulsion taking the 6U cubesat from near the Earth to its final asteroid destination and the Lunar Flashlight sail will provide the propulsion necessary for its spacecraft to enter lunar orbit. Both projects will use an 85 m2 solar sail developed by NASA MSFC. The NEA Scout and Lunar Flashlight flight systems are based on a 6U cubesat form factor, with a stowed envelope of 10 x 20 x 30 cm and a mass of less than 12 kg. The solar sail for NEA Scout and Lunar Flashlight will be based on the technology developed and flown by the NASA NanoSail‐D and The Planetary Society's Lightsail‐A. Four 7 m stainless steel booms wrapped on two spools (two overlapping booms per spool) will be motor deployed and pull the sail from its stowed volume. The sail material will be 3 micron CP1, an aluminized polyimide that was extensively tested for solar sail applications. The sail will spooled rather than Z‐folded. This paper will describe both the Lunar Flashlight and NEA Scout missions and their solar sails.

Johnson, Les↗
NASA NTRS2003

Software for Displaying Data from Planetary Rovers

Science Activity Planner (SAP) DownlinkBrowser is a computer program that assists in the visualization of processed telemetric data [principally images, image cubes (that is, multispectral images), and spectra] that have been transmitted to Earth from exploratory robotic vehicles (rovers) on remote planets. It is undergoing adaptation to (1) the Field Integrated Design and Operations (FIDO) rover (a prototype Mars-exploration rover operated on Earth as a test bed) and (2) the Mars Exploration Rover (MER) mission. This program has evolved from its predecessor - the Web Interface for Telescience (WITS) software - and surpasses WITS in the processing, organization, and plotting of data. SAP DownlinkBrowser creates Extensible Markup Language (XML) files that organize data files, on the basis of content, into a sortable, searchable product database, without the overhead of a relational database. The data-display components of SAP DownlinkBrowser (descriptively named ImageView, 3DView, OrbitalView, PanoramaView, ImageCubeView, and SpectrumView) are designed to run in a memory footprint of at least 256MB on computers that utilize the Windows, Linux, and Solaris operating systems.

Powell, Mark↗
DOE OSTI2021

Long-period Jovian Tilts the Orbits of Two sub-Neptunes Relative to Stellar Spin Axis in Kepler-129

We present the discovery of Kepler-129 d (P{sub d}=7.2{sub -0.3}{sup +0.4} yr, msini{sub d}=8.3{sub -0.7}{sup +1.1} M{sub Jup}, e{sub d}=0.15{sub -0.05}{sup +0.07}) based on six years of radial-velocity observations from Keck/HIRES. Kepler-129 also hosts two transiting sub-Neptunes: Kepler-129 b (P {sub b} = 15.79 days, r {sub b} = 2.40 ± 0.04 R {sub ⊕}) and Kepler-129 c (P {sub c} = 82.20 days, r {sub c} = 2.52 ± 0.07 R {sub ⊕}) for which we measure masses of m {sub b} < 20 M {sub ⊕} and m{sub c}=43{sub -12}{sup +13} M{sub ⊕}. Kepler-129 is a hierarchical system consisting of two tightly packed inner planets and a massive external companion. In such a system, two inner planets precess around the orbital normal of the outer companion, causing their inclinations to oscillate with time. Based on an asteroseismic analysis of Kepler data, we find tentative evidence that Kepler-129 b and c are misaligned with stellar spin axis by ≳38°, which could be torqued by Kepler-129 d if it is inclined by ≳19° relative to inner planets. Using N-body simulations, we provide additional constraints on the mutual inclination between Kepler-129 d and inner planets by estimating the fraction of time during which two inner planets both transit. The probability that two planets both transit decreases as their misalignment with Kepler-129 d increases. We also find a more massive Kepler-129 c enables the two inner planets to become strongly coupled and more resistant to perturbations from Kepler-129 d. The unusually high mass of Kepler-129 c provides a valuable benchmark for both planetary dynamics and interior structure, since the best-fit mass is consistent with this 2.5 R {sub ⊕} planet having a rocky surface.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS2004

Forward Contamination of the Moon and Mars: Implications for Future Life Detection Missions

NASA and ESA have outlined new visions for solar system exploration that will include a series of lunar robotic missions to prepare for, and support a human return to the Moon, and future human exploration of Mars and other destinations. One of the guiding principles for exploration is to pursue compelling scientific questions about the origin and evolution of life. The search for life on objects such as Mars will require that all spacecraft and instrumentation be sufficiently cleaned and sterilized prior to launch to ensure that the scientific integrity of extraterrestrial samples is not jeopardized by terrestrial organic contamination. Under COSPAR's current planetary protection policy for the Moon, no sterilization procedures are required for outbound lunar spacecraft. Nonetheless, future in situ investigations of a variety of locations on the Moon by highly sensitive instruments designed to search for biologically derived organic compounds would help assess the contamination of the Moon by lunar spacecraft. These studies could also provide valuable "ground truth" data for Mars sample return missions and help define planetary protection requirements for future Mars bound spacecraft carrying life detection experiments. In addition, studies of the impact of terrestrial contamination of the lunar surface by the Apollo astronauts could provide valuable data to help refine future Mars surface exploration plans for a human mission to Mars.

Glavin, Daniel P.↗
NASA NTRS2012

Next Gen NEAR: Near Earth Asteroid Human Robotic Precursor Mission Concept

Asteroids have long held the attention of the planetary science community. In particular, asteroids that evolve into orbits near that of Earth, called near-Earth objects (NEO), are of high interest as potential targets for exploration due to the relative ease (in terms of delta V) to reach them. NASA's Flexible Path calls for missions and experiments to be conducted as intermediate steps towards the eventual goal of human exploration of Mars; piloted missions to NEOs are such example. A human NEO mission is a valuable exploratory step beyond the Earth-Moon system enhancing capabilities that surpass our current experience, while also developing infrastructure for future mars exploration capabilities. To prepare for a human rendezvous with an NEO, NASA is interested in pursuing a responsible program of robotic NEO precursor missions. Next Gen NEAR is such a mission, building on the NEAR Shoemaker mission experience at the JHU/APL Space Department, to provide an affordable, low risk solution with quick data return. Next Gen NEAR proposes to make measurements needed for human exploration to asteroids: to demonstrate proximity operations, to quantify hazards for human exploration and to characterize an environment at a near-Earth asteroid representative of those that may be future human destinations. The Johns Hopkins University Applied Physics Laboratory has demonstrated exploration-driven mission feasibility by developing a versatile spacecraft design concept using conventional technologies that satisfies a set of science, exploration and mission objectives defined by a concept development team in the summer of 2010. We will describe the mission concept and spacecraft architecture in detail. Configuration options were compared with the mission goals and objectives in order to select the spacecraft design concept that provides the lowest cost, lowest implementation risk, simplest operation and the most benefit for the mission implementation. The Next Gen NEAR spacecraft was designed to support rendezvous with a range of candidate asteroid targets and could easily be launched with one of several NASA launch vehicles. The Falcon 9 launch vehicle supports a Next Gen NEAR launch to target many near-Earth asteroids under consideration that could be reached with a C3 of 18 km2/sec2 or less, and the Atlas V-401 provides added capability supporting launch to NEAs that require more lift capacity while at the same time providing such excess lift capability that another payload of opportunity could be launch in conjunction with Next Gen NEAR. Next Gen NEAR will measure and interact with the target surface in ways never undertaken at an asteroid, and will prepare for first human precursor mission by demonstrating exploration science operations at an accessible NEO. This flexible mission and spacecraft design concept supports target selection based on upcoming Earth-based observations and also provides opportunities for co-manifest & international partnerships. JHU/APL has demonstrated low cost, low risk, high impact missions and this mission will help to prepare NASA for human NEO exploration by combining the best of NASA s human and robotic exploration capabilities.

Rivkin, Andrew S.↗
NASA NTRS2018

Chlorine Isotopic Compositions of Apatite in Apollo 14 Rocks: Evidence for Widespread Vapor-Phase Metasomatism on the Lunar Nearside ~4 Billion Years Ago

Compared to most other planetary materials in the Solar System, some lunar rocks display high delta (sup 37) Cl signatures. Loss of Cl in a H<<Cl environment has been invoked to explain the heavy signatures observed in lunar samples, either during volcanic eruptions onto the lunar surface or during large scale degassing of the lunar magma ocean. To explore the conditions under which Cl isotope fractionation occurred in lunar basaltic melts, five Apollo 14 crystalline samples were selected (14053,19, 14072,13, 14073,9, 14310,171 along with basaltic clast 14321,1482) for in situ analysis of Cl isotopes using secondary ion mass spectrometry. Cl isotopes were measured within the mineral apatite, with delta (sup 37) Cl values ranging from +14.6 ± 1.6 per mille to +40.0 ± 2.9 per mille. These values expand the range previously reported for apatite in lunar rocks, and include some of the heaviest Cl isotope compositions measured in lunar samples to date. The data here do not display a trend between increasing rare earth elements contents and delta (sup 37) Cl values, reported in previous studies. Other processes that can explain the wide inter- and intra-sample variability of delta (sup 37) Cl values are explored. Magmatic degassing is suggested to have potentially played a role in fractionating Cl isotope in these samples. Degassing alone, however, could not create the wide variability in isotopic signatures. Our favored hypothesis, to explain small scale heterogeneity, is late-stage interaction with a volatile-rich gas phase, originating from devolatilization of lunar surface regolith rocks ~4 billion years ago. This period coincides with vapor-induced metasomastism recorded in other lunar samples collected at the Apollo 16 and 17 landing sites, pointing to the possibility of widespread volatile-induced metasomatism on the lunar nearside at that time, potentially attributed to the Imbrium formation event.

apatit↗
NASA NTRS2000

Numerical Modeling Studies of Wake Vortex Transport and Evolution Within the Planetary Boundary Layer

The fundamental objective of this research is study behavior of aircraft wake vortices within atmospheric boundary layer (ABL) in support of developing the system, Aircraft VOrtex Spacing System (AVOSS), under NASA's Terminal Area Productivity (TAR) program that will control aircraft spacing within the narrow approach corridors of airports. The purpose of the AVOSS system is to increase airport capacity by providing a safe reduction in separation of aircraft compared to the now-existing flight rules. In our first funding period (7 January 19994 - 6 April 1997), we have accomplished extensive model development and validation of ABL simulations. Using the validated model, in our second funding period (7 April 1997 - 6 April 2000) we have investigated the effects of ambient atmospheric turbulence on vortex decay and descent, Crow instability, and wake vortex interaction with the ground. Recognizing the crucial influence of ABL turbulence on wake vortex behavior, we have also developed a software generating vertical profiles of turbulent kinetic energy (TKE) or energy dissipation rate (EDR), which are, in turn, used as input data in the AVOSS prediction algorithms.

Lin, Yuh-Lang↗
NASA NTRS2004

Reflectance Experiment Laboratory (RELAB) Description and User's Manual

Spectroscopic data acquired in the laboratory provide the interpretive foundation upon which compositional information about unexplored or unsampled planetary surfaces is derived from remotely obtained reflectance spectra. The RELAB is supported by NASA as a multi-user spectroscopy facility, and laboratory time can be made available at no charge to investigators who are in funded NASA programs. RELAB has two operational spectrometers available to NASA scientists: 1) a near- ultraviolet, visible, and near-infrared bidirectional spectrometer and 2) a near- and mid- infrared FT-IR spectrometer. The overall purpose of the design and operation of the RELAB bidirectional spectrometer is to obtain high precision, high spectral resolution, bidirectional reflectance spectra of earth and planetary materials. One of the key elements of its design is the ability to measure samples using viewing geometries specified by the user. This allows investigators to simulate, under laboratory conditions, reflectance spectra obtained remotely (i.e., with spaceborne, telescopic, and airborne systems) as well as to investigate geometry dependent reflectance properties of geologic materials. The Nicolet 740 FT-IR spectrometer currently operates in reflectance mode from 0.9 to 25 Fm. Use and scheduling of the RELAB is monitored by a 4-member advisory committee. NASA investigators should direct inquiries to the Science Manager or RELAB Operator.

Pieters, Carle M.↗
NASA NTRS2008

Modeling of the Ablation of Fibrous Materials in the Knudsen Regime

During atmospheric entry of planetary probes, the thermal protection system (TPS) of the probe is exposed to high temperatures under low pressures. In these conditions, carbonous TPS materials undergo gasification in the Knudsen regime leading to mass loss and wall recession called ablation. This work aims to improve the understanding of materiaVenvironment interactions through a study of the coupling between carbon dioxide transport in the Knudsen regime, heterogeneous oxidation of carbon, and sutface recession. A 3D Monte-Carlo simulation tool is used for this study. The fibrous architecture of the materiils, consisting of high porosity random array of carbon fibers, is numerically reproduced on a 3D Cartesian grid. Mass transport in the Knudsen regime from the boundary layer to the surface, and inside this porous material is simulated by random walk. A reaction probability is used to simulate the heterogeneous oxidation reaction. The surface recession is followed by front tracking using a simplified marching cube approach. The output data of the simulations are ablation velocity and dynamic evolution of the material porosity. A parametric study is carried out to analyze the material behavior as a function of Knudsen number for the porous media (length of the mean free path compared to the mean pore diameter) and the intrinsic reactivity of the carbon fibers. The results enable extrapolation of laboratory experimental data to actual entry conditions.

Lachaud, J.↗
NASA NTRS1977

Lander Locations, Mars Physical Ephemeris, and Solar System Parameters: Determination from Viking Lander Tracking Data

Radio tracking data from the Viking landers have been analyzed to determine the parameters of the Mars physical ephemeris, the radii of Mars at the landing sites, and the lander locations. The orientation of the Mars rotation axis, referred to the 1950.0 earth mean equator, equinox, and epoch, was determined to be 317.340+/-0.003 degrees right ascension and 52.710+/-0.002degrees declination. The planet's rotation period was determined to be 24 h, 37 min, 22.663+/-0.002 s. Analyses indicate that the determination of the motions of the Mars rotation axis will require additional tracking data. The Mars radii at the sites of landers 1 and 2 are 3389.38+/-0.06 km and 3381.91+/-0.08 km, respectively. The areocentric location of lander 1 is 22.272+/-0.002 degrees N, 47.94+/-0.2 degrees W. The lander 2 location is 47.670+/-0.002 degrees N, 225.71+/-0.2 degrees W. The areocentric right ascensions of the landers are determined to be 277.314+/-0.002 degrees for lander 1 and 99.546+/-0.002degrees for lander 2 at 0000 hours, January 1, 1977 (Julian date 2443144.57). Possible determinations of relativity parameters, solar oblateness, asteroid mass, and variations of the universal gravitational constant, from their effects on the planetary motions, will require the additional tracking data of the Viking extended mission.

Mayo, A. P.↗
NASA NTRS1971

Our present state of ignorance of the outer planets and their satellites.

Although the outer solar system contains the bulk of the angular momentum of the system and a huge fraction of the total planetary mass, very little is actually known about it. Massive Jupiter, with its low mean density and huge red spot (possibly a Taylor column), shows a complex rotational pattern as a result of three rotating systems, each having a different period. Atmospheric scattering of the reflected solar radiation makes spectral interpretation uncertain. Imprecisions in the Bond albedo cause discrepancies between actual and predicted solar energy absorbed. Saturn is similar to Jupiter in massiveness, low density, atmospheric aerosols, and albedo. Its rings are believed to be largely water ice. To date, no evidence of radiation belts, analogous to Jupiter's, exists for Saturn, Uranus, or Neptune. Methane and hydrogen have been detected in the atmospheres of all these planets, but the mole fraction of hydrogen is lower in the atmospheres of Uranus and Neptune. Uranus' 98 degree inclination will provide basis for study of its atmospheric circulation. Our knowledge of Pluto is restricted to the sparsest physical data.

Rea, D. G.↗
NASA NTRS1994

Precise mean sea level measurements using the Global Positioning System

This paper describes the results of a sea level measurement test conducted off La Jolla, California, in November of 1991. The purpose of this test was to determine accurate sea level measurements using a Global Positioning System (GPS) equipped buoy. These measurements were intended to be used as the sea level component for calibration of the ERS 1 satellite altimeter. Measurements were collected on November 25 and 28 when the ERS 1 satellite overflew the calibration area. Two different types of buoys were used. A waverider design was used on November 25 and a spar design on November 28. This provided the opportunity to examine how dynamic effects of the measurement platform might affect the sea level accuracy. The two buoys were deployed at locations approximately 1.2 km apart and about 15 km west of a reference GPS receiver located on the rooftop of the Institute of Geophysics and Planetary Physics at the Scripps Institute of Oceanography. GPS solutions were computed for 45 minutes on each day and used to produce two sea level time series. An estimate of the mean sea level at both locations was computed by subtracting tide gage data collected at the Scripps Pier from the GPS-determined sea level measurements and then filtering out the high-frequency components due to waves and buoy dynamics. In both cases the GPS estimate differed from Rapp's mean altimetric surface by 0.06 m. Thus, the gradient in the GPS measurements matched the gradient in Rapp's surface. These results suggest that accurate sea level can be determined using GPS on widely differing platforms as long as care is taken to determine the height of the GPS antenna phase center above water level. Application areas include measurement of absolute sea level, of temporal variations in sea level, and of sea level gradients (dominantly the geoid). Specific applications would include ocean altimeter calibration, monitoring of sea level in remote regions, and regional experiments requiring spatial and temporal resolution higher than that available from altimeter data.

Kelecy, Thomas M.↗
NASA NTRS1995

X-Ray Emission from the Sun in Its Youth and Old Age

We have obtained ROSAT PSPC (Roentgen Satellite Position Sensitive Proportional Counter) pointed observations of two nearby G stars of ages 70 Myr and 9.5 Gyr that are of unique importance as proxies for the Sun at the two extremes of its main-sequence evolutionary lifetime. The younger star, HD 129333 (EK Dra; G0 V), a rapid rotator with a 2.7 day period, is a strong source with an X-ray luminosity L(x)(0.2-2.4 keV) = (7.5-11.5) x 10(exp 29) erg/s. Modeling suggests a two-temperature corona with T(1) = (2.0 +/- 0.3) x 10(exp 6) K and T(2) = (9.7 +/- 0.3) x 10(exp 6) K (formal uncertainties). A continuous emission measure distribution, increasing to higher temperatures and with a cutoff at (20-30) x 10(exp 6) K, yields even better fits to the data. The old star, beta Hyi (HR 98; G2 IV), represents the Sun in the future, near the end of its hydrogen-core burning stage, when it should be rotating more slowly (present P(rot) = 25.4 day) and should have lower levels of activity. The ROSAT measurements yield L(x) = (0.9-3.0) x 10(exp 27) ergs/s and a rather cool, single coronal temperature of T = (1.7 +/- 0.4) x 10(exp 6) K. For comparison, the Sun has L(x) approx. equal to 2 x 10(exp 27) ergs/s and a coronal temperature of about T = 2 x 10(exp 6) K. These stars provide information on the decline of the stellar (and specifically solar) magnetic activity from extreme youth to old age. HD 129333 is also important in that it yields an estimate of the solar soft X-ray flux in the early solar system at the epoch of the terminal stages of planetary accretion.

Dorren, J. D.↗
NASA NTRS2000

Nanorovers and Subsurface Explorers for Mars

Recent advances in microtechnology and mobile robotics have made it feasible to create extremely small automated or remote-controlled vehicles which open new application frontiers. One of these possible applications is the use of nanorovers (robotic vehicles with a mass of order one kilogram or less) in planetary exploration. NASA and Japan's Institute of Space and Astronautical Science (ISAS) are cooperating on the first mission to collect samples from the surface of an asteroid and return them to Earth for in-depth study. The ISAS MUSES-C mission will be launched on a Japanese launch vehicle in July 2002 from Japan toward a rendez-vous with the asteroid 1989ML in September 2003. A NASA-provided nanorover will conduct in-situ measurements on the surface. With a mass of about one kilogram, the rover experiment will be a direct descendant of the technology used to build the Sojourner rover. The rover will carry three science instruments: (1) a visible imaging camera, (2) a near-infrared point spectrometer, and (3) an alpha X ray spectrometer. The solar-powered rover will move around the surface of 1989ML collecting imagery data, which are complimentary to the spacecraft investigation. The imaging system will be capable of making surface texture, composition, and morphology measurements at resolutions better than one millimeter. The rover will transmit this data to the spacecraft for relay back to Earth. Due to the microgravity environment on 1989ML, the rover has been designed to right itself in case it flips over. Solar panels on four sides of the rover will ensure that enough power will always be available to the rover to activate the motors needed to turn over. Posable struts will allow the rover to position its chassis such that the camera can be pointed straight down at the surface or straight up at the sky.

Wilcox, Brian H.↗
NASA NTRS2002

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.↗