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Showing papers in "Earth Moon and Planets in 2015"


Journal ArticleDOI
TL;DR: In this article, the authors investigated the linearized equations of motion relative to the equilibrium points and characteristic equations and found that the distribution of characteristic multipliers of periodic orbits around the equilibrium point correspond to each other.
Abstract: In this study, equilibrium points and periodic orbits in the potential field of asteroids are investigated. We present the linearized equations of motion relative to the equilibrium points and characteristic equations. We find that the distribution of characteristic multipliers of periodic orbits around the equilibrium point and the distribution of eigenvalues of the equilibrium point correspond to each other. The distribution of eigenvalues of the equilibrium point confirms the topology and the stability of periodic orbits around the equilibrium point.

37 citations


Journal ArticleDOI
TL;DR: In this paper, a European airborne meteor observation campaign was organized, supported by ground-based observations, and two aircraft were deployed from Kiruna, Sweden, carrying six scientists, 19 cameras and eight crew members.
Abstract: On 8 October 2011, the Draconid meteor shower (IAU $$\#8$$ , DRA) was predicted to cause two brief outbursts of meteors, visible from locations in Europe. For the first time, a European airborne meteor observation campaign was organized, supported by ground-based observations. Two aircraft were deployed from Kiruna, Sweden, carrying six scientists, 19 cameras and eight crew members. The flight geometry was chosen such that it was possible to obtain double-station observations of many meteors. The instrument setup on the aircraft as well as on the ground is described in full detail. The main peak from 1900-dust ejecta happened at the predicted time and at the predicted rate. The second peak was observed from the earlier flight and from the ground, and was caused most likely by trails ejected in the nineteenth century. A total of 250 meteors were observed, for which light curve data were derived. The trajectory, velocity, deceleration and orbit of 35 double station meteors were measured. The magnitude distribution index was high, as a result of which there was no excess of meteors near the horizon. The light curve proved to be extremely flat on average, which was unexpected. Observations of spectra allowed us to derive the compositional information of the Draconids meteoroids and showed an early release of sodium, usually interpreted as resulting from fragile meteoroids. Lessons learned from this experience are derived for future airborne meteor shower observation campaigns.

25 citations


Journal ArticleDOI
TL;DR: In this article, the authors reported the detection of two transient luminous events recorded on the lunar surface on February 6, 2013, at 06:29:56.7 UT and April 14, 2013 20:00:45.4 from the Atlas Golf Marrakech observatory in Morocco.
Abstract: We report the detection of two transient luminous events recorded on the lunar surface on February 6, 2013, at 06:29:56.7 UT and April 14, 2013, 20:00:45.4 from the Atlas Golf Marrakech observatory in Morocco. Estimated visual magnitudes are 9.4 ± 0.2 and 7.7 ± 0.2. We show that these events have the typical characteristics of impact flashes generated by meteoroids impacting the lunar surface, despite proof using two different telescopes is not available. Assuming these events were lunar impact flashes, meteoroid masses are 0.3 ± 0.05 and 1.8 ± 0.3 kg, corresponding to diameters of 7–8 and 14–15 cm for a density of 1500 kg m−3. The meteoroids would have produced craters of about 2.6 ± 0.3 and 4.4 ± 0.3 m in diameter. We then present a method based on the identification of lunar features illuminated by the Earthshine to determine the position of the flash. The method does not require any information about the observation geometry or lunar configuration. The coordinates are respectively 08.15° ± 0.15°S 59.1° ± 0.15°E and 26.81° ± 0.15°N 09.10° ± 0.15°W. Further improvement on the determination of the flash position is necessary for seismological applications. This studies demonstrates that permanent lunar impact flashes observation programs may be run in different parts of the globe using mid-sized telescopes. We call for the development of an international lunar impact astronomical detection networks that would represent an opportunity for scientific and cultural developments in countries where astronomy is under-represented.

22 citations


Journal ArticleDOI
TL;DR: In this article, a multiluid MHD model is proposed to separate the dynamics of the solar wind ions and the pick-up ions created through photoionization and electron impact ionization in the coma of the comet.
Abstract: Periodic comets move around the Sun on elliptical orbits As such comet 67P/Churyumov-Gerasimenko (hereafter 67P) spends a portion of time in the inner solar system where it is exposed to increased solar insolation Therefore given the change in heliocentric distance, in case of 67P from aphelion at 568 AU to perihelion at ~124 AU, the comet’s activity—the production of neutral gas and dust—undergoes significant variations As a consequence, during the inbound portion, the mass loading of the solar wind increases and extends to larger spatial scales This paper investigates how this interaction changes the character of the plasma environment of the comet by means of multifluid MHD simulations The multifluid MHD model is capable of separating the dynamics of the solar wind ions and the pick-up ions created through photoionization and electron impact ionization in the coma of the comet We show how two of the major boundaries, the bow shock and the diamagnetic cavity, form and develop as the comet moves through the inner solar system Likewise for 67P, although most likely shifted back in time with respect to perihelion passage, this process is reversed on the outbound portion of the orbit The presented model herein is able to reproduce some of the key features previously only accessible to particle-based models that take full account of the ions’ gyration The results shown herein are in decent agreement to these hybrid-type kinetic simulations

21 citations


Journal ArticleDOI
TL;DR: In this article, the authors examined the temporal development of the HF-induced Langmuir and ion turbulences from 1 ms to many minutes after the turn-on of the high-power, high-frequency (HF) beam in the F region.
Abstract: The Arecibo high-power, high-frequency (HF) facility and 430 MHz radar are used to examine the temporal development of the HF-induced Langmuir and ion turbulences from 1 ms to many minutes after the turn-on of the HF beam in the F region. All HF observations begin in a smooth, stratified, stable plasma. “Cold start” HF transmissions are employed to avoid remnant irregularities from prior HF transmissions. HF-excited plasma line (HFPL) and ion line echoes are used to monitor the evolution of the turbulence. In the evening/nighttime the HFPL develops in three reproducible stages. Over time scales of 0 to 10–20 ms (possibly 40 ms), the smooth plasma conditions are maintained, and the results are consistent with theoretical models of the excitation of strong Langmuir turbulence near HF reflection. This entails the initiation of the so-called “caviton production cycle.” The turbulence from the parametric decay instability is detected at lower altitudes where the radar wave vector matches those of the HF-enhanced waves. The data suggests that the two processes coexist in the region in between. After ~40 ms the “overshoot process” begins and consists of a downward extension of the HFPL from the HF reflection region to heights ~1.1 km below followed by a retreat back to the reflection region. The whole overshoot process takes place over a time scale of ~3 s. Thereafter the echo remains near HF reflection for 20–90 s after HF turn-on. The HFPL echo subsequently breaks up into patches because of the formation of large-scale electron density structures in the plasma. New kinetic models indicate that suprathermal electrons excited in the plasma by, for example, caviton burn-out serve to regulate plasma turbulence in the modified ionospheric volume.

21 citations


Journal ArticleDOI
TL;DR: In this paper, the results of ionospheric HF heating experiments to generate artificial acoustic-gravity waves (AGW) and traveling ionosphere disturbances (TID) were conducted at the High-frequency Active Auroral Research Program facility in Gakona, Alaska.
Abstract: We report the results of our ionospheric HF heating experiments to generate artificial acoustic-gravity waves (AGW) and traveling ionospheric disturbances (TID), which were conducted at the High-frequency Active Auroral Research Program facility in Gakona, Alaska. Based on the data from UHF radar, GPS total electron content, and ionosonde measurements, we found that artificial AGW/TID can be generated in ionospheric modification experiments by sinusoidally modulating the power envelope of the transmitted O-mode HF heater waves. In this case, the modulation frequency needs to be set below the characteristic Brunt–Vaisala frequency at the relevant altitudes. We avoided potential contamination from naturally-occurring AGW/TID of auroral origin by conducting the experiments during geomagnetically quiet time period. We determine that these artificial AGW/TID propagate away from the edge of the heated region with a horizontal speed of approximately 160 m/s.

12 citations


Journal ArticleDOI
TL;DR: In this paper, a method based on digital elevation model (DEM) data from lunar orbiter laser altimeter was proposed to detect the lunar craters automatically, where all overlapping depressions were detected in order (larger depressions first, then the smaller ones).
Abstract: Impact-induced circular structures, known as craters, are the most obvious geographic and geomorphic features on the Moon. The studies of lunar carters’ patterns and spatial distributions play an important role in understanding geologic processes of the Moon. In this paper, we proposed a method based on digital elevation model (DEM) data from lunar orbiter laser altimeter to detect the lunar craters automatically. Firstly, the DEM data of study areas are converted to a series of spatial fields having different scales, in which all overlapping depressions are detected in order (larger depressions first, then the smaller ones). Then, every depression’s true boundary is calculated by Fourier expansion and shape parameters are computed. Finally, we recognize the craters from training sets manually and build a binary decision tree to automatically classify the identified depressions into craters and non-craters. In addition, our crater-detection method can provides a fast and reliable evaluation of ages of lunar geologic units, which is of great significance in lunar stratigraphy studies as well as global geologic mapping.

10 citations


Journal ArticleDOI
TL;DR: In this article, the solar wind flow around a cometary atmosphere is calculated using the three-dimensional magnetohydrodynamic model developed by the authors, and the behavior of the flowfield and the magnetic field disturbed by the cometary outflow is analyzed.
Abstract: The solar wind flow around a cometary atmosphere is calculated using the three-dimensional magnetohydrodynamic model developed by the authors. Emphasis is placed on the case of low-activity comets in which some special features, both quantitative and qualitative, are inherent. The behavior of the flowfield and the magnetic field disturbed by the cometary outflow is analyzed. Some similarity laws that govern the pattern of the interaction between the solar wind and a cometary atmosphere are derived on the basis of the calculated results.

9 citations


Journal ArticleDOI
TL;DR: In this paper, a series of experiments employing the HF transmitter of the High Frequency Active Auroral Research Program (HAARP) to generate and study strong Langmuir turbulence (SLT) in the interaction region of overdense ionospheric plasma is reported.
Abstract: We report results from a recent series of experiments employing the HF transmitter of the High Frequency Active Auroral Research Program (HAARP) to generate and study strong Langmuir turbulence (SLT) in the interaction region of overdense ionospheric plasma. The Modular UHF Ionospheric Radar (MUIR) located at the HAARP facility is used as the primary diagnostic. Short pulse, low duty cycle experiments are used to avoid generation of artificial field-aligned irregularities and isolate ponderomotive plasma turbulence effects. The HF pump frequency is close to the 3rd gyro-harmonic frequency and the HF pointing angle and MUIR look angle are between the HF Spitze angle and Magnetic Zenith angle. Plasma line spectra measured simultaneously in different spots of the interaction region display differences dependent on the aspect angle of the HF pump beam in the boresight direction and the pointing angle of the MUIR diagnostic radar. Outshifted Plasma Lines, cascade, collapse, coexistence, spectra are observed in agreement with existing theory and simulation results of Strong Langmuir Turbulence in ionospheric interaction experiments. It is found that SLT at HAARP is most readily observed at a HF pointing angle of 11° and UHF observation angle of 15°, which is consistent with the magnetic zenith effect as documented in previous works and optimal orientation of the refracted HF electric field vector.

9 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present results from the High-Frequency Active Auroral Research Program (HAARP) experiments using a twisted beam excitation mode, where the heating region produced is in the shape of a ring as opposed to the more traditional “solid spot” region from a pencil beam.
Abstract: Nonlinear interactions of high power HF radio waves in the ionosphere provide aeronomers with a unique space-based laboratory capability. The High-Frequency Active Auroral Research Program (HAARP) in Gakona, Alaska is the world’s largest heating facility, yielding effective radiated powers in the gigawatt range. New results are present from HAARP experiments using a “twisted beam” excitation mode. Analysis of twisted beam heating shows that the SEE results obtained are identical to more traditional patterns. One difference in the twisted beam mode is the heating region produced is in the shape of a ring as opposed to the more traditional “solid spot” region from a pencil beam. The ring heating pattern may be more conducive to the creation of stable artificial airglow layers because of the horizontal structure of the ring. The results of these runs include artificial layer creation and evolution as pertaining to the twisted beam pattern. The SEE measurements aid the interpretation of the twisted beam interactions in the ionosphere.

8 citations


Journal ArticleDOI
TL;DR: In this article, the effect of various sensor parameters on the polarization of the received radar signal over the same targets using two different SAR data was analyzed and the inconsistent results of Chandrayaan-1 Mini-SAR and LRO Mini-RF data were observed over all five craters.
Abstract: The paper presents a case study of inconsistent behaviour of Chandrayaan-1 Mini-SAR and LRO Mini-RF data over south polar lunar craters. The paper includes analysis of Stokes parameters and characterization of received time-varying electromagnetic fields over the south pole lunar craters. For the study, Chandrayaan-1 Mini-SAR and LRO Mini-RF data at 2.38 GHz are used. Total five lunar craters in south polar region are analyzed to study the effect of various parameters on the polarization of the signal. We have compared linear horizontal (LH) and linear vertical (LV) polarization components of received radar signal over the same targets using two different SAR data. Ratios of received LH to LV components are also derived over the five craters. It is observed that Chandrayaan-1 Mini-SAR is receiving high LH component as compared to LV component. This is not consistent with the scattering theory (Fawwaz et al. in Microwave remote sensing active and passive, Artech House Inc., New York, 1981), which states that for incidence angle greater than 15°, the vertical polarized component of a received signal should be always high as compared to horizontal polarized component over rough surfaces. These inconsistent results of Chandrayaan-1 Mini-SAR are observed over all five craters. In the paper, various effects of sensor parameters like incident angle, ellipticity angle, orientation angle etc. on scattering mechanism are discussed to understand the inconsistent behaviour of two SAR data over same target.

Journal ArticleDOI
TL;DR: In this article, the authors used optical inversion to estimate the spectrum of high-energy radio wave-excited electron fluxes in Earth's weakly ionized space plasma, which can significantly improve detection of emissions near ionization threshold and confirm depth of penetration of accelerated electrons many km below the excitation altitude.
Abstract: Wave particle interactions, an essential aspect of laboratory, terrestrial, and astrophysical plasmas, have been studied for decades by transmitting high power HF radio waves into Earth’s weakly ionized space plasma, to use it as a laboratory without walls. Application to HF electron acceleration remains an active area of research (Gurevich in Usp Fizicheskikh Nauk 177(11):1145–1177, 2007) today. HF electron acceleration studies began when plasma line observations proved (Carlson et al. in J Atmos Terr Phys 44:1089–1100, 1982) that high power HF radio wave-excited processes accelerated electrons not to ~eV, but instead to −100 times thermal energy (10 s of eV), as a consequence of inelastic collision effects on electron transport. Gurevich et al (J Atmos Terr Phys 47:1057–1070, 1985) quantified the theory of this transport effect. Merging experiment with theory in plasma physics and aeronomy, enabled prediction (Carlson in Adv Space Res 13:1015–1024, 1993) of creating artificial ionospheres once ~GW HF effective radiated power could be achieved. Eventual confirmation of this prediction (Pedersen et al. in Geophys Res Lett 36:L18107, 2009; Pedersen et al. in Geophys Res Lett 37:L02106, 2010; Blagoveshchenskaya et al. in Ann Geophys 27:131–145, 2009) sparked renewed interest in optical inversion to estimate electron spectra in terrestrial (Hysell et al. in J Geophys Res Space Phys 119:2038–2045, 2014) and planetary (Simon et al. in Ann Geophys 29:187–195, 2011) atmospheres. Here we present our unpublished optical data, which combined with our modeling, lead to conclusions that should meaningfully improve future estimates of the spectrum of HF accelerated electron fluxes. Photometric imaging data can significantly improve detection of emissions near ionization threshold, and confirm depth of penetration of accelerated electrons many km below the excitation altitude. Comparing observed to modeled emission altitude shows future experiments need electron density profiles to derive more accurate HF electron flux spectra.

Journal ArticleDOI
TL;DR: A review of the most significant advances in our understanding of lunar geoscience, including the assessment of water ice at the poles, the detection of new elements and minerals relating to exposed interior materials, and the calculation of highly accurate gravity models, is presented in this article.
Abstract: The twenty first century was an exciting epoch in planetary exploration, when a large number of lunar scientific achievements were accomplished. New missions in the first decade of the twenty first century have herald a new and exciting phase in lunar exploration, including LRO, LCROSS, the dual GRAIL orbiters, Kaguya, Chandrayaan 1, and the Chang’e series. Here we review the most significant advances in our understanding of lunar geoscience, including the assessment of water ice at lunar poles, the detection of new elements and minerals relating to exposed interior materials, the calculation of highly accurate gravity models, and the detection of subsurface interfaces probably related to basaltic strata formed in distinct episodes. In this paper we emphasize the importance of integrated approaches to the analysis of these large yield of new lunar data, through comparison and integration. By integrating a range of diverse technologies and approaches, this paper reviews new understanding of lunar processes, including the confirmation of the presence of water ice at the poles, the interactions between solar wind and surface oxides, and an improved model of lunar interior structures.

Journal ArticleDOI
TL;DR: The theoretical concepts behind this application and the main features of MESCAL are presented, showcasing how radio recordings are handled, prepared for analysis, and used to train the aforementioned neural networks.
Abstract: Meteor Scanning Algorithms (MESCAL) is a software application for automatic meteor detection from radio recordings, which uses self-organizing maps and feedforward multi-layered perceptrons. This paper aims to present the theoretical concepts behind this application and the main features of MESCAL, showcasing how radio recordings are handled, prepared for analysis, and used to train the aforementioned neural networks. The neural networks trained using MESCAL allow for valuable detection results, such as high correct detection rates and low false-positive rates, and at the same time offer new possibilities for improving the results.

Journal ArticleDOI
TL;DR: In this article, low-velocity collisions between granular aggregates are a possible mechanism that allows the growth of small planetary objects or the aggregation after catastrophic or high-energy collisions.
Abstract: Quasi-2D, low-velocity experiments of colliding granular projectiles against granular targets were performed by means of a 7 m-long Hele-Shaw cell. The processes involved in the crater-opening mechanism of low-velocity granular-against-granular collisions are described. We show that the crater is opened mainly by a compaction process of the target. The projectile is fragmented and its lower section suffers a severe compaction; this projectile remnant forms a central dome or peak inside the crater. When the target reaches its maximum degree of compaction, the excess of momentum generates fast avalanches sliding on the slopes of the confined material, and exerts pressure on the crater walls, increasing its diameter. We propose that low-velocity collisions between granular aggregates are a possible mechanism that allows the growth of small planetary objects or the aggregation after catastrophic or high-energy collisions.

Journal ArticleDOI
TL;DR: In this paper, the effect and extent of fragmentation on trail echoes observed by the high power large aperture radars using the 53 MHz Gadanki MST radar was studied and it was reported that the evolution of these trails can be explained with the help of fragmentation.
Abstract: Meteoroids are responsible for deposition of thousands of kilograms of annual mass flux in the Earth’s upper atmosphere but the disintegration mechanisms of these bodies, and hence their composition, still remains a subject of debate in the meteor radar community The role and significance of fragmentation as a meteoroid disintegration mechanism has been of particular interest in the past few years but in contrast to the head echoes, relatively little work has been done to study the effect and extent of fragmentation on trail echoes observed by the high power large aperture radars Using the 53 MHz Gadanki MST radar, we present examples of radar meteor trails whose evolution cannot be explained with just the aid of classical meteor ablation theory These examples are analyzed and discussed on a case-by-case basis and it is reported that the evolution of these trails can be explained with the help of fragmentation This study will form the basis for future modeling efforts of fragmenting meteor trails and has important implications on the form in which the meteoroid mass is deposited in the upper atmosphere

Journal ArticleDOI
TL;DR: In this paper, a comprehensive study of artificial ionospheric signal generation in the ULF/VLF bands at SURA facility in Russia was conducted during the past 4 years, and the influence of geomagnetic activity on the characteristics of artificial low-frequency signals under the background of increasing solar activity was investigated.
Abstract: A comprehensive study of artificial ionospheric signal generation in the ULF/VLF bands at SURA facility in Russia was conducted during the past 4 years We investigated the influence of geomagnetic activity on the characteristics of artificial low-frequency signals under the background of increasing solar activity No correlation of artificial ULF signals with variations of Earth’s magnetic field was observed for weak geomagnetic disturbances \((Kp \le 3)\) while the VLF signals increased in the growth phase of the geomagnetic perturbation In case of strong magnetic storm \((Kp \ge 5+)\) a tendency of the amplitude of the ULF/VLF signals decrease with increasing magnetic disturbance was observed Sometimes, the modulation of artificial ULF signals with a period of 15–30 s was detected in the decay phase of magnetic storms During storm time, a change in the polarization of artificial VLF emissions was detected The right polarization becomes predominant Interpretation of observed peculiarities of artificial VLF signals is given in the context of the physical mechanism of ionospheric current drive by RF pumping

Journal ArticleDOI
TL;DR: In this article, the nonlinear wave structures of ion acoustic waves in magnetized plasma comprising ions, non-extensive distributed electrons and kinematic viscosity are investigated through dynamical study.
Abstract: The nonlinear wave structures of ion acoustic waves in magnetized plasma comprising ions, non-extensive distributed electrons and kinematic viscosity are investigated through dynamical study. In a bounded cylindrical geometry Zakharov–Kuznestov–Burger (ZKB) equation is derived, for the first time, using reductive perturbation technic. System of coupled nonlinear ordinary differential equations is derived from ZKB equation and is solved numerically using fourth order Runge–kutta method. Equilibrium points are obtained and the features are studied dynamically in the neighbourhood of these points. With the variation of the non-extensive parameter and the kinematic viscosity parameter some important features in the nonlinear waves like oscillatory shocks to steady state propagation and vis-a-vis steady state propagation to oscillatory shocks emerge. When the values of the non-extensive parameter decrease, the phase portrait of the system shows that the change from stable spiral to stable closed and stable to unstable equilibrium happens . When the effect of dissipative term i.e. kinematic viscosity is considered some other significant features also evolve .The reduction of the value of kinematic viscosity results the change in nature of the waves from oscillatory shocks to periodic one.

Journal ArticleDOI
TL;DR: In this paper, a survey of Ca-, Al-rich inclusions in GRV 023155 (CV3) and GRV 050179 (CM2) suggests that Type A and spinel-pyroxene inclusions are common in these two meteorites.
Abstract: Two new carbonaceous chondrites, GRV 023155 and GRV 050179, collected from the Grove Mountains (GRV), Antarctica, have been classified as the oxidized CV3 and CM2 chondrites, respectively. A total of 9 Ca-, Al-rich inclusions (CAIs) were found in the two meteorites. Most of the inclusions are extensively altered, with phyllosilicates commonly found in the alteration assemblages of CAIs, chondrules and matrix in the GRV 050179 CM2 chondrites, suggesting that aqueous alteration occurred on the host meteorite parent body. In contrast, feldspathoids and hedenbergite were identified in the CAIs from GRV 023155. The FeO-rich phases in the CAIs from GRV 023155 indicate alteration of these CAIs happened under high oxygen fugacity. All 9 inclusions can be classified as Type A or spinel-pyroxene rich inclusions, and they probably represent a continuum of solar nebular condensation. The survey of Ca-, Al-rich inclusions in GRV 023155 (CV3) and 050179 (CM2) suggests that Type A and spinel-pyroxene inclusions are common in these two meteorites.

Journal ArticleDOI
TL;DR: In this paper, the authors proposed a mechanism for simultaneous sound with passing of large meteors based on the existence of ELF/VLF radio signals, which could not be generated by other sources like lightning, has a frequency range between several Hertz to 500 Hz, and so could be missed with noises produced by electrical machines.
Abstract: For a long time, the generation mechanism of simultaneous sound with passing of large meteors was a research edge until a reasonable mechanism was proposed for that. This mechanism is based on the existence of ELF/VLF radio signals. This research that aims for detection of these signals archives an improvement over previous works. The signal was found on the extremely low frequency (ELF) band which could not be generated by other sources like lightning, has a frequency range between several Hertz to 500 Hz, and so could be missed with noises produce by electrical machines. The new signal is presented at this work has a good correlation with synchronized visual data that were collected on the peak of Geminids 2011 meteor shower.

Journal ArticleDOI
TL;DR: In this article, a small outburst activity of the 2011 Draconid meteor shower has been observed from Gadanki (13.5676 $$^\circ$$� N, 79.2672 $$^''circ$$¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯ E) MST radar.
Abstract: Motivated by several predictions, a small outburst activity of the 2011 Draconid meteor shower has been observed from Gadanki (13.5 $$^\circ$$ N, 79.2 $$^\circ$$ E) MST radar. We detected head echoes and Range Spread Trail Echoes (RSTE) in multiple range gates along with beat pattern echoes. The observed echoes are consistent with meteoroid fragmentation and the light curve shapes examined, which show the evidence of fragmentation irregularities. The mean height of the Draconids is found to be 95 km, which is on an average few kilometers higher than the sporadic meteors of comparable Signal to Noise Ratio (SNR). The results consist of a 740 sample statistical studies, lead to conclude that a quarter of the Draconid radar meteor events included in this study exhibit fragmentation, manifested as non-uniform light curves—implying that the form of meteoroid mass flux into the upper atmosphere goes well beyond simple ablation. A few events are suggestive of differential ablation.


Journal ArticleDOI
TL;DR: In this article, a relatively unexplored area located some 33.4 geodetic km away from the central floor of Euclides, in the NE direction, precisely at −6.62° Latitude and −29.89° Longitude.
Abstract: This study focuses on a relatively unexplored area located some 33.4 geodetic km away from the central floor of Euclides, in the NE direction, precisely at −6.62° Latitude and −29.89° Longitude. Land-based CCD observations of this area showed a small group of dome-like structures situated on an elevated basaltic platform. One hypothesis is that these features represent a series of mounds made up of a collection of undifferentiated crater materials or ejecta as described by USGS (Geologic Atlas of the Moon. Department of Interior, US Geological Survey—I-458, 1965). This hypothesis is tested against an alternative one in that the area shows the presence of domes that are partly covered by these ejecta. The present spectrometric results place the basalt within the chosen AOI subset in the low-Ti category (1–5 wt% TiO2) and a FeO abundance wt% of between 12 and 14. Spectrometrically, similar dome features have been observed by other investigators near the Milichus/Tobias Mayer regions. A possible classification for this feature would be DW/1a/6h/8j. Details of the cluster analysis used for raster classification is presented as an effective approach to discriminate between different classes of the lunar surface. This approach was used to map the lunar soil geology over the selected showing better lunar geological information than the current mapping information available by USGS. This same approach can be used to effectively map out other regions of the lunar surface.

Journal ArticleDOI
TL;DR: The large overlaps, the multi viewing, and the high ground resolution of the images taken by the Apollo MC in generating an accurate and reliable surface of the Moon are taken advantage of.
Abstract: The last three Apollo lunar missions (15, 16, and 17) carried an integrated photogrammetric mapping system of a metric camera (MC), a high-resolution panoramic camera, a star camera, and a laser altimeter. Recently images taken by the MC were scanned by Arizona State University (ASU); these images contain valuable information for scientific exploration, engineering analysis, and visualization of the Moon’s surface. In this article, we took advantage of the large overlaps, the multi viewing, and the high ground resolution of the images taken by the Apollo MC in generating an accurate and reliable surface of the Moon. We started by computing the relative positions and orientations of the exposure stations through a rigorous photogrammetric bundle adjustment process. We then generated a surface model using a hierarchical correlation-based matching algorithm. The matching algorithm was implemented in a multi-photo scheme and permits the exclusion of obscured pixels. The generated surface model was registered with LOLA topographic data and the comparison between the two surfaces yielded an average absolute difference of 36 m. These results look very promising and demonstrate the effectiveness of the proposed algorithm in accounting for depth discontinuities, occlusions, and image-signal noise.